U.S. patent number 10,381,859 [Application Number 15/697,949] was granted by the patent office on 2019-08-13 for wireless power supply system, power transmitter, and power transmission method.
This patent grant is currently assigned to FUJITSU LIMITED. The grantee listed for this patent is FUJITSU LIMITED. Invention is credited to Kiyoto Matsui, Akiyoshi Uchida.
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United States Patent |
10,381,859 |
Matsui , et al. |
August 13, 2019 |
Wireless power supply system, power transmitter, and power
transmission method
Abstract
A wireless power supply system includes: a power transmitter;
and power receivers configured to receive power through magnetic
field resonance or electric field resonance. The transmitter groups
the receivers into first groups based on degrees of coupling
between the transmitter and the respective receivers in an initial
state. The transmitter calculates, for the respective first groups,
charging times required to charge the receivers, and a first total
charging time for the first groups. The transmitter sets degrees of
coupling greater than or equal to the degrees of coupling in the
initial state, and again groups the receivers into second groups
based on the set degrees. The transmitter calculates, for the
respective second groups, charging times required to charge the
receivers and a second total for the second groups, and starts to
transmit the power when the second total time is less than or equal
to the first total time.
Inventors: |
Matsui; Kiyoto (Miki,
JP), Uchida; Akiyoshi (Akashi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
FUJITSU LIMITED |
Kawasaki-shi, Kanagawa |
N/A |
JP |
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Assignee: |
FUJITSU LIMITED (Kawasaki,
JP)
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Family
ID: |
56919907 |
Appl.
No.: |
15/697,949 |
Filed: |
September 7, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170366034 A1 |
Dec 21, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2015/057841 |
Mar 17, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J
7/00034 (20200101); H02J 7/025 (20130101); H02J
50/12 (20160201); H02J 50/80 (20160201); H02J
50/40 (20160201); H02J 7/00 (20130101); H04B
5/0037 (20130101) |
Current International
Class: |
H02J
7/02 (20160101); H02J 7/00 (20060101); H02J
50/12 (20160101); H04B 5/00 (20060101); H02J
50/40 (20160101); H02J 50/80 (20160101) |
Field of
Search: |
;320/108 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2009-268311 |
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Nov 2009 |
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JP |
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2013-034367 |
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Feb 2013 |
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JP |
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2010106636 |
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Sep 2010 |
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WO |
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2013146929 |
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Oct 2013 |
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WO |
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Other References
International Search Report for International Application No.
PCT/JP2015/057841 dated Jun. 9, 2015. cited by applicant.
|
Primary Examiner: Muralidar; Richard V
Attorney, Agent or Firm: Katz, Quintos & Hanson, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation application of International
Application PCT/JP2015/057841 filed on Mar. 17, 2015 and designated
the U.S., the entire contents of which are incorporated herein by
reference.
Claims
What is claimed is:
1. A wireless power supply system comprising: a power transmitter
including a primary-side resonant coil and configured to transmit
electric power; and a plurality of power receivers including
secondary-side resonant coils configured to receive the electric
power from the primary-side resonant coil through magnetic field
resonance or electric field resonance generated with the
primary-side resonant coil, wherein the power transmitter groups
the plurality of power receivers into a plurality of first groups
based on degrees of coupling between the power transmitter and the
respective power receivers in an initial state, wherein the power
transmitter calculates, for the respective first groups, charging
times required to charge all the power receivers, and calculates a
first total charging time obtained by totaling the charging times
for all the first groups, wherein the power transmitter sets, to
the power receivers, degrees of coupling that are greater than or
equal to the degrees of coupling in the initial state, wherein the
power transmitter again groups the plurality of power receivers
into a plurality of second groups based on the set degrees of
coupling, wherein the power transmitter calculates, for the
respective second groups, charging times required to charge all the
power receivers, and calculates a second total charging time
obtained by totaling the charging times for the second groups, and
wherein the power transmitter starts to transmit the electric power
when the second total charging time is less than or equal to the
first total charging time.
2. The wireless power supply system according to claim 1, wherein
the power transmitter obtains the degrees of coupling based on
received electric power of the respective power receivers.
3. The wireless power supply system according to claim 1, wherein
the power receivers include adjustment units configured to adjust
the degrees of coupling with the power transmitter, and wherein the
power transmitter causes the adjustment units to set the degrees of
coupling that are greater than or equal to the degrees of coupling
in the initial state.
4. The wireless power supply system according to claim 3, wherein
the power transmitter adjusts the adjustment units such that the
degrees of coupling become maximums.
5. The wireless power supply system according to claim 3, wherein
the adjustment units adjusts angles of the secondary-side resonant
coils with respect to the power receivers.
6. The wireless power supply system according to claim 1, wherein
the power transmitter groups the plurality of power receivers by
separating the degrees of coupling for respective predetermined
ranges, wherein, when the second total charging time is longer than
the first total charging time, the power transmitter generates a
plurality of third groups by moving a second group, whose change
amount of the degrees of coupling for moving to a second group one
level below is smallest among the plurality of second groups, to
the second group one level below, a number of the third groups
being less than a number of the second groups, wherein the power
transmitter calculates a third total charging time obtained by
totaling charging times for all the third groups, and wherein the
power transmitter starts to transmit the electric power when the
third total charging time is less than or equal to the first total
charging time.
7. The wireless power supply system according to claim 1, wherein,
when the second total charging time is longer than the first total
charging time and a number of the second groups is greater than a
number of the first groups, the power transmitter groups the
plurality of power receivers into a plurality of third groups
obtained by degrees of coupling, which are greater than or equal to
the degrees of coupling in the initial state and less than or equal
to the set degrees of coupling, to start to transmit the electric
power, a total charging time for the third groups being shortest
among third groups whose number of groups is equal to the number of
the first groups.
8. The wireless power supply system according to claim 1, wherein,
when the second total charging time is longer than the first total
charging time, the power transmitter groups the plurality of power
receivers into a plurality of third groups obtained by degrees of
coupling, which are greater than or equal to the degrees of
coupling in the initial state and less than or equal to the set
degrees of coupling, to start to transmit the electric power, an
average degree of coupling for the third groups being largest.
9. The wireless power supply system according to claim 6, wherein,
when the third total charging time is longer than the first total
charging time and a number of the third groups is greater than a
number of the first groups, the power transmitter groups the
plurality of power receivers into a plurality of fourth groups
obtained by degrees of coupling, which are greater than or equal to
the degrees of coupling in the initial state and less than or equal
to the set degrees of coupling, to start to transmit the electric
power, a total charging time for the fourth groups being shortest
among fourth groups whose number of groups is equal to the number
of the first groups.
10. The wireless power supply system according to claim 6, wherein,
when the third total charging time is longer than the first total
charging time, the power transmitter groups the plurality of power
receivers into a plurality of fourth groups obtained by degrees of
coupling, which are greater than or equal to the degrees of
coupling in the initial state and less than or equal to the set
degrees of coupling, to start to transmit the electric power, an
average degree of coupling for the fourth groups being largest.
11. The wireless power supply system according to claim 10, wherein
the power receivers further include resonant coils configured to
receive the electric power through magnetic field resonance or
electric field resonance generated with the secondary-side resonant
coils or include induction coils configured to receive the electric
power through electromagnetic induction from the secondary-side
resonant coils.
12. A power transmitter, including a primary-side resonant coil,
for transmitting electric power to a plurality of power receivers
including secondary-side resonant coils configured to receive the
electric power from the primary-side resonant coil through magnetic
field resonance or electric field resonance generated with the
primary-side resonant coil, wherein the power transmitter groups
the plurality of power receivers into a plurality of first groups
based on degrees of coupling between the power transmitter and the
respective power receivers in an initial state, wherein the power
transmitter calculates, for the respective first groups, charging
times required to charge all the power receivers, and calculates a
first total charging time obtained by totaling the charging times
for all the first groups, wherein the power transmitter sets, to
the power receivers, degrees of coupling that are greater than or
equal to the degrees of coupling in the initial state, wherein the
power transmitter again groups the plurality of power receivers
into a plurality of second groups based on the set degrees of
coupling, wherein the power transmitter calculates, for the
respective second groups, charging times required to charge all the
power receivers, and calculates a second total charging time
obtained by totaling the charging times for the second groups, and
wherein the power transmitter starts to transmit the electric power
when the second total charging time is less than or equal to the
first total charging time.
13. A power transmission method in a wireless power supply system,
the wireless power supply system including a power transmitter
including a primary-side resonant coil and configured to transmit
electric power; and a plurality of power receivers including
secondary-side resonant coils configured to receive the electric
power from the primary-side resonant coil through magnetic field
resonance or electric field resonance generated with the
primary-side resonant coil, the power receivers including
adjustment units configured to adjust degrees of coupling with the
power transmitter, the power transmission method comprising:
causing the power transmitter to group the plurality of power
receivers into a plurality of first groups based on degrees of
coupling between the power transmitter and the respective power
receivers in an initial state; causing the power transmitter to
calculate, for the respective first groups, charging times required
to charge all the power receivers, and to calculate a first total
charging time obtained by totaling the charging times for all the
first groups; causing the power transmitter to adjust the
adjustment units to set the degrees of coupling that are greater
than or equal to the degrees of coupling in the initial state;
causing the power transmitter to again group the plurality of power
receivers into a plurality of second groups based on the set
degrees of coupling; causing the power transmitter to calculate,
for the respective second groups, charging times required to charge
all the power receivers, and to calculate a second total charging
time obtained by totaling the charging times for the second groups;
and causing the power transmitter to start to transmit the electric
power when the second total charging time is less than or equal to
the first total charging time.
Description
FIELD
The embodiment discussed herein relates to a wireless power supply
system, a power transmitter, and a power transmission method.
BACKGROUND
A power transmitting apparatus that includes a power transmission
side communication unit that communicates with one or more power
receiving apparatuses that receive transmitted power and includes a
power transmission unit that transmits power to the one or more
power receiving apparatuses in a non-contact manner is known in the
related art. The power transmitting apparatus includes an
allocating unit that divides transmission of power from the power
transmission unit to the power receiving apparatuses in a plurality
of dividing periods for each predetermined period and allocates to
the one or more power receiving apparatuses one of the dividing
periods. The power transmitting apparatus includes a power
transmission control unit that selectively transmits power to the
one or more power receiving apparatuses in a non-contact manner for
a dividing period based on the allocation result in the allocating
unit (for example, see Patent Document 1).
In the above system including the power transmitting apparatus and
the power receiving apparatuses, coupling coefficients between the
power transmitting apparatus and the power receiving apparatuses
are set to be fixed values in accordance with types or the like of
the power receiving apparatus.
However, the coupling coefficients may vary depending on positional
relationships or the like between the power transmitting apparatus
and the power receiving apparatuses or the like. Therefore, it is
difficult for the above system to efficiently transmit power from
the power transmitting apparatus to the power receiving
apparatuses.
RELATED-ART DOCUMENTS
Patent Documents
[Patent Document 1] Japanese Laid-open Patent Publication No.
2009-268311
SUMMARY
According to an aspect of the embodiment, a wireless power supply
system includes: a power transmitter including a primary-side
resonant coil and configured to transmit electric power; and a
plurality of power receivers including secondary-side resonant
coils configured to receive the electric power from the
primary-side resonant coil through magnetic field resonance or
electric field resonance generated with the primary-side resonant
coil. The power transmitter groups the plurality of power receivers
into a plurality of first groups based on degrees of coupling
between the power transmitter and the respective power receivers in
an initial state. The power transmitter calculates, for the
respective first groups, charging times required to charge all the
power receivers, and calculates a first total charging time
obtained by totaling the charging times for all the first groups.
The power transmitter sets, to the power receivers, degrees of
coupling that are greater than or equal to the degrees of coupling
in the initial state. The power transmitter again groups the
plurality of power receivers into a plurality of second groups
based on the set degrees of coupling. The power transmitter
calculates, for the respective second groups, charging times
required to charge all the power receivers, and calculates a second
total charging time obtained by totaling the charging times for the
second groups. The power transmitter starts to transmit the
electric power when the second total charging time is less than or
equal to the first total charging time.
The object and advantages of the invention will be realized and
attained by means of the elements and combinations particularly
pointed out in the claims. It is to be understood that both the
foregoing general description and the following detailed
description are exemplary and explanatory and are not restrictive
of the invention.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1A is a diagram schematically illustrating one example of a
wired power transmission system;
FIG. 1B is a diagram schematically illustrating one example of a
wireless power transmission system;
FIG. 2A is a diagram schematically illustrating one example of a
two-dimensional wireless power transmission system;
FIG. 2B is a diagram schematically illustrating one example of a
three-dimensional wireless power transmission system;
FIG. 3 is a block diagram schematically illustrating one example of
a wireless power transmission system;
FIG. 4A is a diagram (1) for describing a modified example of
transmission coils in the wireless power transmission system of
FIG. 3;
FIG. 4B is a diagram (2) for describing a modified example of
transmission coils in the wireless power transmission system of
FIG. 3;
FIG. 4C is a diagram (3) for describing a modified example of
transmission coils in the wireless power transmission system of
FIG. 3;
FIG. 5A is a circuit diagram (1) illustrating an example of an
independent resonant coil;
FIG. 5B is a circuit diagram (2) illustrating an example of the
independent resonant coil;
FIG. 5C is a circuit diagram (3) illustrating an example of the
independent resonant coil;
FIG. 5D is a circuit diagram (4) illustrating an example of the
independent resonant coil;
FIG. 6A is a circuit diagram (1) illustrating an example of the
resonant coil connected to a load or a power supply;
FIG. 6B is a circuit diagram (2) illustrating an example of the
resonant coil connected to the load or the power supply;
FIG. 6C is a circuit diagram (3) illustrating an example of the
resonant coil connected to the load or the power supply;
FIG. 6D is a circuit diagram (4) illustrating an example of the
resonant coil connected to the load or the power supply;
FIG. 7A is a diagram (1) for describing an example of controlling a
magnetic field by a plurality of power transmitters;
FIG. 7B is a diagram (2) for describing an example of controlling a
magnetic field by a plurality of power transmitters;
FIG. 7C is a diagram (3) for describing an example of controlling a
magnetic field by the plurality of power transmitters;
FIG. 8A is a diagram (1) for describing wireless power transmission
to the plurality of power receivers;
FIG. 8B is a diagram (2) for describing wireless power transmission
to the plurality of power receivers;
FIG. 8C is a diagram (3) for describing wireless power transmission
to the plurality of power receivers;
FIG. 9A is a diagram (1) for describing one example of a
two-dimensional wireless power transmission method for a plurality
of power receivers;
FIG. 9B is a diagram (2) for describing one example of the
two-dimensional wireless power transmission method for the
plurality of power receivers;
FIG. 10A is a diagram (1) for describing one example of a
three-dimensional wireless power transmission method for a
plurality of power receivers;
FIG. 10B is a diagram (2) for describing one example of the
three-dimensional wireless power transmission method for the
plurality of power receivers;
FIG. 10C is a diagram (3) for describing one example of the
three-dimensional wireless power transmission method for the
plurality of power receivers;
FIG. 11A is a diagram (4) for describing one example of the
three-dimensional wireless power transmission method for a
plurality of power receivers;
FIG. 11B is a diagram (5) for describing one example of the
three-dimensional wireless power transmission method for the
plurality of power receivers;
FIG. 11C is a diagram (6) for describing one example of the
three-dimensional wireless power transmission method for the
plurality of power receivers;
FIG. 12 is a diagram for describing an evaluation index in the
wireless power transmission method according to the embodiment;
FIG. 13A is a diagram (1) for illustrating a first example of the
wireless power transmission method;
FIG. 13B is a diagram (2) for illustrating the first example of the
wireless power transmission method;
FIG. 14A is a diagram (3) for illustrating the first example of the
wireless power transmission method;
FIG. 14B is a diagram (4) for illustrating the first example of the
wireless power transmission method;
FIG. 15A is a diagram (1) for illustrating a second example of the
wireless power transmission method;
FIG. 15B is a diagram (2) for illustrating the second example of
the wireless power transmission method;
FIG. 16A is a diagram (3) for illustrating the second example of
the wireless power transmission method;
FIG. 16B is a diagram (4) for illustrating the second example of
the wireless power transmission method;
FIG. 17 is a diagram illustrating one example of a wireless power
supply system according to the embodiment;
FIGS. 18A to 18C are diagrams illustrating a power receiver;
FIG. 19 is a diagram describing grouping according to a wireless
power transmission method of the embodiment;
FIG. 20 is a flowchart illustrating control contents of a power
transmitter;
FIG. 21 is a flowchart illustrating control contents of the power
transmitter;
FIG. 22 is a diagram illustrating data used for grouping;
FIG. 23 is a flowchart illustrating control contents of each power
receiver;
FIG. 24 is a flowchart illustrating control contents of the power
transmitter according to a first variation example of the
embodiment;
FIG. 25 is a flowchart illustrating control contents of the power
transmitter according to a second variation example of the
embodiment;
FIG. 26 is a diagram illustrating an example of grouping according
to an electric power transmission method of the embodiment;
FIG. 27 is a diagram illustrating an example of grouping according
to an electric power transmission method of the embodiment;
FIG. 28 is a diagram illustrating all the ways of grouping when
power receivers are grouped again through a process of FIG. 24;
FIG. 29 is a diagram illustrating an example of grouping according
to an electric power transmission method of the embodiment;
FIGS. 30A to 30C are diagrams illustrating a power receiver
according to a variation example of the embodiment;
FIGS. 31A and 31B are diagrams illustrating a power receiver
according to a variation example of the embodiment; and
FIG. 32 is a diagram illustrating a wireless power supply system
according to a variation example of the embodiment.
DESCRIPTION OF EMBODIMENT
Hereinafter, an embodiment to which a wireless power supply system,
a power transmitter, and a power transmission method of the present
invention are applied will be described. An object of the
embodiment is to provide a wireless power supply system, a power
transmitter, and a power transmission method that can efficiently
transmit electric power.
Embodiment
Before describing the wireless power supply system, the power
transmitter, and the power transmission method of the embodiment in
detail, a wireless power supply system according to a related art
will be described, with reference to FIG. 1 to FIG. 11C. The
wireless power supply system includes a plurality of power
transmitters and a plurality of power receivers.
FIG. 1A is a diagram schematically illustrating one example of a
wired power transmission (wired power supply) system and FIG. 1B is
a diagram schematically illustrating one example of a wireless
power transmission (wireless power supply) system. In FIG. 1A and
FIG. 1B, reference signs 2A1 to 2C1 respectively denote power
receivers.
Here, the power receiver 2A1 represents, for example, a tablet
computer (tablet) having a power requirement of 10 W, the power
receiver 2B1 represents, for example, a notebook computer having a
power requirement of 50 W, and the power receiver 2C1 represents,
for example, a smartphone having a power requirement of 2.5 W. The
power requirements correspond to, for example, electric powers for
charging rechargeable batteries (secondary batteries) in the
respective power receivers 2A1 to 2C1.
As illustrated in FIG. 1A, generally, when the secondary batteries
of the tablet 2A1 and the smartphone 2C1 are charged, for example,
the tablet 2A1 and the smartphone 2C1 are connected to a USB
(Universal Serial Bus) terminal (or a dedicated power supply or the
like) 3A of a Personal Computer via power supply cables 4A and 4C.
When the secondary battery of the notebook computer 2B1 is charged,
for example, the notebook computer 2B1 is connected to a dedicated
power supply (AC-DC Converter) 3B via a power supply cable 4B.
That is, even for the portable power receivers 2A1 to 2C1, wired
power supply (wired power transmission) is generally performed,
from the USB terminal 3A or the power supply 3B, using the power
supply cables 4A to 4C, as illustrated in FIG. 1A.
With the recent advance in non-contact power supply technology
typified by electromagnetic induction, for example, wireless power
supply (wireless power transmission) has come into practice in a
shaver, an electric toothbrush, and the like. For example, electric
power may be wirelessly transferred from a power transmitter 1A1 to
the tablet 2A1, the notebook computer 2B1, and the smartphone 2C1,
as illustrated in FIG. 1B.
FIG. 2A is a diagram schematically illustrating one example of a
two-dimensional wireless power transmission (two-dimensional
wireless power supply) system, and illustrates, for example, how
electric power is wirelessly transferred through electromagnetic
induction, similarly to, for example, the above-mentioned shaver or
electric toothbrush.
As illustrated in FIG. 2A, when electric power is wirelessly
transferred using electromagnetic induction, electric power may be
supplied only to a power receiver which is nearly in contact with a
power transmitter 1A2 because of the short power transmission
distance even in non-contact power supply.
That is, although electric power may be supplied to a power
receiver (notebook computer) 2B2 placed on the power transmitter
(power receiving mount) 1A2, it is difficult to supply electric
power to a notebook computer 2B3 away from the power receiving
mount 1A2. In this manner, the wireless power transmission system
illustrated in FIG. 2A serves as a two-dimensional wireless power
supply system that enables free arrangement on the power receiving
mount 1A2.
FIG. 2B is a diagram schematically illustrating one example of a
three-dimensional wireless power transmission (three-dimensional
wireless power supply) system, and illustrates, for example, how
electric power is wirelessly transferred using magnetic field
resonance or electric field resonance. As illustrated in FIG. 2B,
when electric power is wirelessly transferred using magnetic field
resonance or electric field resonance, electric power may be
supplied from the power transmitter A2 to a plurality of power
receivers that are located within a predetermined range (inside of
a broken line in FIG. 2B).
That is, electric power may be wirelessly transferred from a power
transmitter A3 to tablets 2A2 and 2A3, the notebook computers 2B2
and 2B3, and a smartphone 2C2 that fall within a predetermined
range. Although FIG. 2B depicts only one power transmitter A3, a
plurality of power transmitters wirelessly transfer electric power
to a plurality of power receivers at various angles and positions,
using magnetic field resonance or electric field resonance.
In this manner, the wireless power transmission system illustrated
in FIG. 2B serves as, for example, a three-dimensional wireless
power supply system that uses magnetic field resonance to enable a
high power transmission efficiency for a space farther than that
using electromagnetic induction.
FIG. 3 is a block diagram schematically illustrating one example of
a wireless power transmission (three-dimensional wireless power
supply) system. In FIG. 3, reference sign 1 denotes a primary side
(a power transmitting side: a power transmitter), and reference
sign 2 denotes a secondary side (a power receiver side: a power
receiver).
As illustrated in FIG. 3, the power transmitter includes a wireless
power transmitting unit 11, a power source unit 12, a control unit
13, and a communication unit 14. In addition, the power receiver 2
includes a wireless power receiving unit 21, a rectifier unit 22, a
control unit 23, and a communication unit 24.
The wireless power transmitting unit 11 includes a first coil (a
power supply coil) 11b and a second coil (a primary-side resonant
coil) 11a, and the receiving unit 21 includes a third coil (a
secondary-side resonant coil) 21a and a fourth coil (a power
extraction coil) 21b.
As illustrated in FIG. 3, the power transmitter 1 and the power
receiver 2 perform energy (electric power) transmission from the
power transmitter 1 to the power receiver 2 through magnetic field
resonance (or electric field resonance) between the primary-side
resonant coil 11a and the secondary-side resonant coil 21a. Note
that electric power may be transmitted from the primary-side
resonant coil 11a to the secondary-side resonant coil 21a not only
through magnetic field resonance but also electric field resonance
or the like. However, the following description will be given
mainly by way of example of magnetic field resonance.
The power transmitter 1 and the power receiver 2 communicate with
each other by the communication unit 14 and the communication unit
24. Note that, a distance of electric power transmission (a power
transmission range) through the primary-side resonant coil 11a of
the power transmitter 1 and the secondary-side resonant coil 21a of
the power receiver 2 is set to be shorter than a distance of
communication (a communication range) through the communication
unit 14 of the power transmitter 1 and the communication unit 24 of
the power receiver 2.
In addition, electric power transmission by the primary-side
resonant coil 11a and the secondary-side resonant coil 21a is
performed by a system (an out-band communication) independent from
communication by the communication units 14 and 24. Specifically,
electric power transmission by the resonant coils 11a and 21a uses,
for example, a frequency band of 6.78 MHz, whereas communication by
the communication units 14 and 24 uses, for example, a frequency
band of 2.4 GHz.
The communication by the communication units 14 and 24 may use, for
example, a DSSS wireless LAN system based on IEEE 802.11b or use
Bluetooth (registered trademark).
The above described wireless power transmission system performs
electric power transmission using magnetic field resonance or
electric field resonance by the primary-side resonant coil 11a of
the power transmitter 1 and the secondary-side resonant coil 21a of
the power receiver 2, for example, with respect to a near field of
a distance of approximately the wavelength of the frequency used.
Accordingly, the range of electric power transmission (a power
transmission range) varies with the frequency used for electric
power transmission.
The power source unit 12 is a high frequency power supply unit that
supplies electric power to the power supply coil (the first coil)
11b. The power supply coil 11b supplies electric power to the
primary-side resonant coil 11a arranged very close to the power
supply coil 11b by using electromagnetic induction. The
primary-side resonant coil 11a transmits electric power to the
secondary-side resonant coil 21a (the power receiver 2) at a
resonance frequency that generates magnetic field resonance between
the resonant coils 11a and 21a.
The secondary-side resonant coil 21a supplies electric power to the
power extraction coil (the fourth coil) 21b arranged very close to
the secondary-side resonant coil 21a, by using electromagnetic
induction. The power extraction coil 21b is connected to the
rectifier unit 22 to extract a predetermined amount of electric
power. The electric power extracted from the rectifier unit 22 is
used, for example, for charging a battery with respect to a battery
(load) 25, as an electric power output to the circuits of power
receiver 2, or the like.
Note that, the power source unit 12 of the power transmitter 1 is
controlled by the control unit 13, and the rectifier unit 22 of the
power receiver 2 is controlled by the control unit 23. Then, the
control unit 13 and the control unit 23 are connected via the
communication units 14 and 24, and adapted to perform various
controls so that electric power transmission from the power
transmitter 1 to the power receiver 2 may be performed in a
preferable state.
FIG. 4A to FIG. 4C are diagrams for describing variation examples
of transmission coils in the wireless power transmission system of
FIG. 3. Note that, FIG. 4A and FIG. 4B depict exemplary three-coil
structures, and FIG. 4C depicts an exemplary two-coil
structure.
Specifically, in the wireless power transmission system illustrated
in FIG. 3, the wireless power transmitting unit 11 includes the
first coil 11b and the second coil 11a, and the power receiving
unit 21 includes the third coil 21a and the fourth coil 21b.
Conversely, in the example of FIG. 4A, the power receiving unit 21
is set as a single coil (a secondary-side resonant coil: an LC
resonator) 21a, and in the example of FIG. 4B, the wireless power
transmitting unit 11 is set as a single coil (a primary-side
resonant coil: an LC resonator) 11a.
Further, in the example of FIG. 4C, the power receiving unit 21 is
set as a single secondary-side resonant coil 21a and the wireless
power transmitting unit 11 is set as a single primary-side resonant
coil 11a. Note that, FIG. 4A to FIG. 4C are merely examples and,
obviously, various modifications may be made.
FIG. 5A to FIG. 5D are circuit diagrams illustrating examples of an
independent resonant coil (the secondary-side resonant coil 21a),
and FIG. 6A to FIG. 6D are circuit diagrams illustrating examples
of a resonant coil (the secondary-side resonant coil 21a) connected
to a load or a power supply.
Note that, FIG. 5A to FIG. 5D correspond to the secondary-side
resonant coil 21a of FIG. 3 and FIG. 4B, and FIG. 6A to FIG. 6D
correspond to the secondary-side resonant coil 21a of FIG. 4A and
FIG. 4C.
In the examples illustrated in FIG. 5A and FIG. 6A, the
secondary-side resonant coil 21a includes a coil (L) 211, a
capacitor (C) 212, and a switch 213 connected in series, in which
the switch 213 is ordinarily in an off-state. In the examples
illustrated in FIG. 5B and FIG. 6B, the secondary-side resonant
coil 21a includes the coil (L) 211 and the capacitor (C) 212
connected in series, and the switch 213 connected in parallel to
the capacitor 212, in which the switch 213 is ordinarily in an
on-state.
In the examples illustrated in FIG. 5C and FIG. 6C, the
secondary-side resonant coil 21a of FIG. 5B and FIG. 6B includes
the switch 213 and the resistance (R) 214 connected in series and
arranged in parallel to the capacitor 212, in which the switch 213
is ordinarily in the on-state.
In the examples of FIG. 5D and FIG. 6D, the secondary-side resonant
coil 21a of FIG. 5B and FIG. 6B includes the switch 213 and another
capacitor (C') 215 connected in series therewith and arranged in
parallel to the capacitor 212, in which the switch 213 is
ordinarily in the on-state.
In each of the secondary-side resonant coils 21a described above,
the switch 213 is set to "off" or "on" so that the secondary-side
resonant coil 21a does not operate under ordinary conditions. The
reason for this is, for example, to prevent heat generation or the
like caused by electric power transmission to a power receiver 2
not in use or to a power receiver 2 out of order.
In the above structure, the primary-side resonant coil 11a of the
power transmitter 1 may also be set similarly as in FIG. 5A to FIG.
5D and FIG. 6A to FIG. 6D. However, the primary-side resonant coil
11a of the power transmitter may be set to operate under ordinary
conditions and may be controlled to be turned on/off by an output
of the power source unit 12. In this case, in the primary-side
resonant coil 11a, the switch 213 is closed in FIG. 5A and FIG.
6A.
In this manner, when a plurality of power receivers 2 are present,
selecting only the secondary-side resonant coil 21a of a
predetermined power receiver 2 to which electric power is to be
transmitted from the power transmitter 1 and making it in an
operable state enables the electric power to be transmitted
(time-division power transmission) to the selected power receiver
2.
FIG. 7A to FIG. 7C are diagrams for describing examples of
controlling a magnetic field by a plurality of power sources. In
FIG. 7A to FIG. 7C, reference signs 1A and 1B denote power
transmitters, and reference sign 2 denotes a power receiver.
As illustrated in FIG. 7A, a primary-side resonant coil 11aA for
power transmission used for magnetic field resonance of the power
transmitter 1A and a primary-side resonant coil 11aB for power
transmission used for magnetic field resonance of the power
transmitter 1B are disposed, for example, so as to be orthogonal to
each other.
Further, the secondary-side resonant coil 21a for power reception
used for magnetic field resonance of the power receiver 2 is
arranged at a different angle (an angle not parallel) at a position
surrounded by the primary-side resonant coils 11aA and 11aB.
Here, the primary-side resonant coils (LC resonators) 11aA and 11aB
may also be provided in a single power transmitter. That is, a
single power transmitter may include a plurality of wireless power
transmitting units 11.
FIG. 7B depicts a situation in which the primary-side resonant
coils 11aA and 11aB output an in-phase magnetic field, and FIG. 7C
depicts a situation in which the primary-side resonant coils 11aA
and 11aB output an opposite phase magnetic field.
For example, by comparing the cases where the two orthogonal
primary-side resonant coils 11aA and 11aB output in-phase magnetic
fields and reverse phase magnetic fields, the combined magnetic
fields are related by a rotation of 90 degrees, and electric power
is transmitted to the power receivers 2 (secondary-side resonant
coils 21a) suited to the orientations of the respective power
receiver 2.
As described above, when electric power by the plurality of power
sources 1A and 1B is transmitted to the power receiver 2 positioned
at any position and an orientation (angle), magnetic fields
generated at the primary-side resonant coils 11aA and 11aB of the
power transmitters 1A and 1B change variously.
The above described wireless power transmission system includes a
plurality of power transmitters and at least one power receiver and
adjusts outputs (strengths and phases) between the plurality of
power transmitters according to a position (X, Y, Z) and an
orientation (.theta.X, .theta.Y, .theta.Z) of the power
receiver.
In addition, it will be seen that, with respect to a
three-dimensional space, for example, three or more power
transmitters are used in the actual three-dimensional space to
adjust the respective output phase differences and the output
intensity ratios so as to control the magnetic field (electric
field) in any direction in the three-dimensional space.
FIG. 8A to FIG. 8C are diagrams for describing wireless power
transmission to a plurality of power receivers. For the sake of
simplicity, although FIG. 8A to FIG. 8C depict only one power
transmitter A and two power receivers (mobile phones) 2A and 2A',
the number of power transmitters and the number and types of power
receivers or the like may obviously vary. That is, assume that one
power transmitter A is used to wirelessly supply electric power to
the two power receivers 2A and 2A', as illustrated in FIG. 8A.
First, when electric power is supplied by time-division power
transmission, the electric power is supplied to only one power
receiver 2A, as illustrated on the left of FIG. 8B, and the
electric power is then supplied to only the other power receiver
2A, as illustrated on the right of FIG. 8B. Note that the same
applies when three or more power receivers are used, and electric
power is wirelessly supplied to the power receivers by sequentially
switching the power receivers to be supplied with the electric
power in a time-division manner.
That is, in time-division power transmission, when a plurality of
power receivers are provided, power receivers to be supplied with
electric power are sequentially selected to allow one power
receiver to always correspond to the power transmitter at a certain
moment. At this time, control may be performed similarly as in, for
example, the case where power transmitters and power receivers are
provided in one-to-one correspondence. However, as a result of time
division, the time taken for power supply (full charging)
corresponds to the number of power receivers, and the time to
supply electric power to two power receivers is therefore twice
that to supply electric power to one power receiver.
Next, when electric power is wirelessly supplied by simultaneous
power transmission, one power transmitter 1A supplies the electric
power to both the two power receivers 2A and 2A', as illustrated in
FIG. 8C. Note that the same applies when three or more power
receivers are used, and the electric power is simultaneously and
wirelessly supplied to the plurality of power receivers.
In this simultaneous power transmission, when, for example, two
power receivers are provided, because electric power is
simultaneously supplied to the two power receivers, and supplying
electric power for a time corresponding to only one power receiver
may be sufficient regardless of the number of power receivers to be
simultaneously supplied with power. Thus, this power supply method
(wireless power transmission method) is desirable in terms of user
benefits.
However, for simultaneous power supply (simultaneous power
transmission) to a plurality of power receivers, control is done
differently from the case of only one power receiver.
FIG. 9A and FIG. 9B are diagrams for describing one example of a
two-dimensional wireless power transmission method for a plurality
of power receivers. FIG. 9A illustrates, for example, how electric
power is wirelessly supplied to two power receivers 2A and 2B
having different power requirements by one power transmitter 1A,
using magnetic field resonance. Referring to FIG. 9B, reference
sign LL0 denotes the overall power transmission efficiency; LLA
denotes the electric power received by the mobile phone 2A; and LLB
denotes the electric power received by the notebook computer
2B.
The power receiver 2A represents, for example, a mobile phone
having a power requirement of 5 W and the power receiver 2B
represents, for example, a notebook computer having a power
requirement of 50 W. For the sake of simplicity, an LC resonator (a
power receiving unit) for the mobile phone 2A and an LC resonator
for the notebook computer 2B have the same specifications.
In the two-dimensional wireless power transmission system, when
electric power is simultaneously and wirelessly supplied to a
plurality of power receivers, the amount of electric power received
by each power receiver may often be different. For example, as
illustrated in FIG. 9A, for a mobile phone having a power
requirement of 5 W and a notebook computer having a power
requirement of 50 W, or even for the same types of power receivers,
the power requirement may be different depending on the remaining
battery level.
Under the circumstances, for example, in the two-dimensional
wireless power transmission system, because the conditions of
distance and orientation of the power receivers 2A and 2B placed on
the power transmitter 1A may have only a small difference, electric
power is equally distributed when they are equipped with power
receiving coils having the same specifications.
Thus, as illustrated in FIG. 9A, even for power receivers 2A and 2B
having power requirements different by 10 times, when, for example,
an output corresponding to a power requirement of 55 W is output
from the power transmitter 1A, the power receivers 2A and 2B each
receive an electric power of 27.5 W.
That is, the mobile phone 2A and the notebook computer 2B include,
for example, secondary-side resonant coils 21a as illustrated in
FIG. 5A, and the inductances of their coils 211 and the
capacitances of their capacitors 212 take equal values.
Specifically, let L.sub.A be the inductance in the power receiving
secondary-side resonant coil of the mobile phone 2A, C.sub.A be its
capacitance, L.sub.B be the inductance in the secondary-side
resonant coil of the notebook computer 2B, and C.sub.B be its
capacitance. In this case, as indicated by reference sign PP0,
L.sub.0C.sub.0=L.sub.AC.sub.A=L.sub.BC.sub.B is satisfied in the
as-is state (the state in which the resonance point is not
shifted).
Accordingly, assuming, for example, that the electric power
transmitted from the power transmitter 1A is 68.75 W and its
efficiency of electric power transmission is 80%, both the mobile
phone 2A and the notebook computer 2B receive an electric power of
27.5 W.
However, because the mobile phone 2A has the power requirement of 5
W and the notebook computer 2B has the power requirement of 50 W,
the resonance point of the power receiving resonant coil of the
mobile phone 2A is shifted to control for a decrease in the
efficiency of electric power reception.
For example, as indicated by the arrow MA in FIG. 9B, the
capacitance C.sub.A in the power receiving secondary-side resonant
coil of the mobile phone 2A is controlled to be lower (or higher)
to make a shift from the resonance point of the power receiving
secondary-side resonant coil that maximizes the efficiency of
electric power reception.
That is, as indicated by the arrow MA in FIG. 9B, intentionally
shifting the resonance conditions (shifting the capacitance
C.sub.A) reduces the Q factor so that the received electric power
LLA of the mobile phone 2A can be gradually decreased from 27.5 W
at the resonance point (P0) and, for example, set to a power
requirement of 5 W.
In this case, most of electric power that is not received by the
mobile phone 2A becomes electric power received by the notebook
computer 2B. That is, obviously, the received electric power LLB of
the notebook computer 2B increases in response to a decrease of
received electric power LLA of the mobile phone 2A, and the overall
efficiency LL0 of electric power transmission in the wireless power
transmission system does not decrease substantially.
In this manner, changing the resonance conditions and,
specifically, changing the capacitance value (capacitance C.sub.A)
of the resonant capacitor (the capacitor) 212 of the power receiver
2A may adjust coupling. As a result it becomes possible to control
the received power to be a desired distribution ratio.
Importantly, even when the efficiency of the power receiver 2A is
reduced, of which the resonance conditions have been changed, the
entire efficiency of electric power transmission and reception of
the system is maintained nearly constant, and the electric power to
the power receiver 2B increases by the amount of reduction in
electric power having reached the power receiver 2A. As a result,
obviously, compared to single-body power supply to only one of the
power receivers 2A and 2B, received electric power may be
distributed at a desired ratio while electric power is supplied to
the entire system (both the power receivers 2A and 2B) at nearly
the same efficiency.
Next, a three-dimensional wireless power transmission system will
be described. FIG. 10A to FIG. 11C are diagrams for describing one
example of a three-dimensional wireless power transmission method
for a plurality of (two) power receivers. For the sake of
simplicity, although FIG. 10A to FIG. 11C depict only one power
transmitter 1A and two power receivers 2A and 2B, the same applies
when a plurality of power transmitters and three or more power
receivers are used.
Here, FIG. 10A to FIG. 10C depict the case where the distance from
the power transmitter 1A to the two power receivers 2A and 2B is
300 mm, and FIG. 11A to FIG. 11C depict the case where the distance
from the power transmitter 1A to the two power receivers 2A and 2B
is 500 mm.
Referring to FIGS. 10B and 11B, reference sign LA denotes the
efficiency of electric power reception of the power receiver 2A; LB
denotes the efficiency of electric power reception of the power
receiver 2B; PM denotes the transmitted electric power (maximum
power transmission output) that can be output from the power
transmitter 1A; RP denotes the required transmitted power; and TP
denotes the overall efficiency of electric power reception (overall
efficiency).
Further, the reference sign P0 denotes the case where electric
power is transmitted at a ratio between the power requirements of
the power receivers 2A and 2B of 1:1 (9 W:9 W); and the reference
sign P1 denotes the case where electric power is transmitted at a
ratio between the power requirements of the power receivers 2A and
2B of 2:1 (12 W:6 W). Note that FIG. 10B and FIG. 11B are diagrams
with normalization assuming that the power ratio of 1:1 is
"1.00."
That is, assuming that the electric power transmitted to the two
power receivers 2A and 2B is 18 W, the case where the power
requirements of both the power receivers 2A and 2B are 9 W and the
case where the power requirement of the power receiver 2A is 12 W
and the power requirement of the power receiver 2B is 6 W will be
considered hereinafter. Note that the maximum power transmission
output of the power transmitter A is assumed to be limited to 50 W
in accordance with, for example, the specifications of the power
transmitter, regulations stipulated in for radio waves, or the
like.
A case where the distance from the power transmitter 1A to the two
power receivers 2A and 2B is 300 mm (they are relatively close to
each other) will be considered below with reference to FIG. 10A to
FIG. 10C. First, when the power requirements of both the power
receivers 2A and 2B to be simultaneously supplied with electric
power are 9 W, i.e., when electric power is transmitted at a power
ratio of 1:1 (9 W:9 W), the efficiencies of electric power
reception of both the power receivers 2A and 2B are assumed to be,
for example, 30.1% (the overall efficiency (TP) is assumed to be
60.2%).
Then, as illustrated in P0 of FIG. 10B and FIG. 10C, setting the
power transmission output of the power transmitter 1A to 29.9 W
allows each of the power receivers 2A and 2B to receive an electric
power of 29.9.times.0.301.apprxeq.9 W.
When the power requirement of the power receiver 2A is 12 W and the
power requirement of the power receiver 2B is 6 W, i.e., when
electric power is transmitted at a power ratio of 2:1 (12 W:6 W),
the resonance point of the power receiving secondary-side resonant
coil of the power receiver 2B is shifted, as described with
reference to FIG. 9A and FIG. 9B.
That is, electric power is simultaneously supplied to the power
receivers 2A and 2B by shifting the resonance point of the power
receiving secondary-side resonant coil of the power receiver 2B to
control the power distribution ratio to decrease the efficiency of
electric power reception of the power receiver 2B (increase the
efficiency of electric power reception of the power receiver
2A).
Specifically, as illustrated in P1 of FIG. 10B and FIG. 10C, the
resonance point of the power receiving secondary-side resonant coil
of the power receiver 2B is shifted to set the efficiency of
electric power reception of the power receiver 2A to be 39.5% and
the efficiency of electric power reception of the power receiver 2B
to be 19.7%. At this time, the overall efficiency (TP) is
59.2%.
As illustrated in FIG. 10C, setting the power transmission output
of the power transmitter 1A to 30.4 W allows the power receiver 2A
to receive an electric power of 30.4.times.0.395.apprxeq.12 W and
the power receiver 2B to receive an electric power of
30.4.times.0.197.apprxeq.6 W.
Here, when the distance from the power transmitter 1A to the two
power receivers 2A and 2B is 300 mm, the required transmission
power RP of the power transmitter 1A is lower than a maximum power
transmission output of 50 W for both power transmission at an
electric power ratio of 1:1 (29.9 W) and power transmission at an
electric power ratio of 2:1 (30.4 W).
In addition, the overall efficiency TP is substantially constant in
power transmission at the electric power ratio of 1:1 (60.2%) and
power transmission at the electric power ratio of 2:1 (59.2%).
Therefore, when the distance from the power transmitter 1A to the
two power receivers 2A and 2B is 300 mm (they are relatively close
to each other), both power transmission at the electric power ratio
of 1:1 and power transmission between the electric power ratio of
2:1 may be implemented by simultaneous power supply.
Next, a case where the distance from the power transmitter 1A to
the two power receivers 2A and 2B is 500 mm (they are relatively
distant from each other) will be considered next with reference to
FIG. 11A to FIG. 11C. First, when the power requirements of both
the power receivers 2A and 2B to be simultaneously supplied with
power are 9 W, i.e., when electric power is transmitted at an
electric power ratio of 1:1 (9 W:9 W), the efficiencies of electric
power reception of both the power receivers 2A and 2B are assumed
to be, for example, 18.2% (the overall efficiency (TP) is assumed
to be 36.4%).
Then, as illustrated in P0 of FIG. 11B and FIG. 11C, setting the
power transmission output of the power transmitter 1A to 49.5 W
allows each of the power receivers 2A and 2B to receive electric
power of 49.5.times.0.182.apprxeq.9 W. In this case, the required
transmitted power RP (49.5 W) of the power transmitter 1A is lower
than a maximum power transmission output of 50 W, and electric
power may be simultaneously supplied to the power receivers 2A and
2B.
Next, when the power requirement of the power receiver 2A is 12 W
and the power requirement of the power receiver 2B is 6 W (the
power ratio is 2:1), the resonance point of the power receiving
secondary-side resonant coil of the power receiver 2B is shifted to
control the power distribution ratio to decrease the efficiency of
electric power reception of the power receiver 2B (increase the
efficiency of electric power reception of the power receiver 2A),
as described above.
Specifically, as depicted in P1 of FIG. 11B and FIG. 11C, the
resonance point of the power receiving secondary-side resonant coil
of the power receiver 2B is shifted such that the efficiency of
electric power reception of the power receiver 2A is 21.2% and the
efficiency of electric power reception of the power receiver 2B is
10.6%. At this time, the overall efficiency (TP) is 31.8%.
However, to set the received electric power of the power receiver
2A to be 12 W (.apprxeq.56.6.times.0.212), the required transmitted
power RP of the power transmitter 1A is set to 56.6 W, which is
higher than a maximum power transmission output of 50 W. It is
therefore difficult to simultaneously supply electric power to the
two power receivers 2A and 2B.
Note that when the power transmission output of the power
transmitter 1A is not limited to 50 W in accordance with, for
example, the specifications of the power transmitter or regulations
stipulated for radio waves, the power transmitter 1A may preferably
have its power transmission output increased to tolerate a required
transmitted power RP of 56.6 W.
In the following, a wireless power transmission method, a power
transmitter, and a power transmission method according to the
embodiment will be described in detail with reference to the
accompanying drawings. Note that the embodiment is applicable to a
wireless power transmission system that uses at least one power
transmitter to wirelessly transmit electric power to a plurality of
power receivers.
An example in which electric power is wirelessly transmitted by
using magnetic field resonance (magnetic field sympathetic
vibration) from one power transmitter to a plurality of (two to
five) power receivers will be described in the following. However,
according to the embodiment, electric power may be transmitted by
two or more power transmitters, as described with reference to FIG.
7A to FIG. 7C. Further, the embodiment is similarly applicable to a
wireless power transmission system that uses electric field
resonance (electric field sympathetic vibration) instead of
magnetic field resonance.
In the wireless power supply system, the power transmitter, and the
power transmission method of the embodiment, kQ (kQ value) is
employed as an evaluation index for wireless power transmission
(wireless power supply). Here, k (k value) indicates the degree of
coupling of electromagnetic fields, and the larger the k value, the
higher the degree of coupling. The k value is an example of a
coupling coefficient. Further, Q (Q factor) indicates the degree of
losses in an electromagnetic field, and the larger the Q factor,
the lower the degree of loss.
That is, kQ is represented by the following formula (1). Here, Qt
is the Q factor of a power transmitter and Qr is the Q factor of a
power receiver. kQ=k {square root over (QtQr)} (1)
Further, k is represented by the following formula (2). Here, Mtr
is the mutual inductance between a power transmitter and a power
receiver, Lt is the self-inductance of the power transmitter, and
Lr is the self-inductance of the power receiver.
##EQU00001##
Further, Q is represented by the following formula (3). Here,
.omega. represents the angular frequency, Rt represents losses in
the resonant coil of the power transmitter, and Rr represents
losses in the resonant coil of the power receiver.
.omega..times..times..times..omega..times..times. ##EQU00002##
FIG. 12 is a diagram for describing an evaluation index in the
wireless power transmission method of the embodiment and
illustrates a relationship between the kQ value (the product of k
and Q) and the ideal efficiency in one power transmitter and one
power receiver.
FIG. 12 represents the kQ value on the abscissa and the efficiency
on the ordinate. That is, according to the embodiment, the kQ value
for one power transmitter and one power receiver representing
characteristics as illustrated in FIG. 12, for example, is applied
to electric power transmission between at least one power
transmitter and at least two (a plurality of) power receivers.
In, for example, designing a wireless power supply system, a kQ
value is possible as an index for determining the efficiency of
electric power transmission. Here, as illustrated in FIG. 12, in,
for example, wireless power supply at Power Transmission:Power
Reception=1:1, a theoretical relationship is established for the
efficiency and the kQ value, and a theoretical maximum efficiency
of electric power reception may be estimated by evaluating the kQ
value.
FIG. 13A to FIG. 14B are diagrams for describing a first example of
a wireless power transmission method and for describing a wireless
power transmission method in a three-dimensional wireless power
transmission method of the first example.
Although FIG. 13A to FIG. 14B illustrate only one power transmitter
1A and two power receivers 2A and 2B for the sake of simplicity,
the same applies to a plurality of power transmitter and three or
more power receivers.
Here, FIG. 13A and FIG. 13B illustrate a case where the distance
from the power transmitter 1A to the two power receivers 2A and 2B
is 300 mm and correspond to FIG. 10A and FIG. 10B described above.
Further, FIG. 14A and FIG. 14B illustrate a case where the distance
from the power transmitter 1A to the two power receivers 2A and 2B
is 500 mm and correspond to FIG. 11A and FIG. 11B described
above.
Referring to FIG. 13B and FIG. 14B, the reference sign LA denotes
the efficiency of electric power reception of the power receiver
2A; the reference sign LB denotes the efficiency of electric power
reception of the power receiver 2B; the reference sign PM denotes
the maximum power transmission output of the power transmitter 1A;
the reference sign RP denotes the required transmitted power; and
the reference sign TP denotes the overall efficiency.
Further, the reference sign P0 denotes a case where electric power
is transmitted at a ratio between the power requirements of the
power receivers 2A and 2B of 1:1 (9 W:9 W); and the reference sign
P1 denotes a case where electric power is transmitted at a ratio
between the power requirements of the power receivers 2A and 2B of
2:1 (12 W:6 W). Note that FIG. 13B and FIG. 14B are diagrams with
normalization assuming that the power ratio of 1:1 is "1.00."
Here, because FIG. 13A and FIG. 13B correspond to FIG. 10A and FIG.
10B described above and FIG. 14A and FIG. 14B correspond to FIG.
11A and FIG. 11B described above, repetitive descriptions thereof
will be omitted as appropriate.
First, as illustrated in FIG. 13A and FIG. 13B, when the distance
from the power transmitter 1A to the two power receivers 2A and 2B
is 300 mm, the k value and the Q factor are k=0.0065 and Q=510. In
this case, the kQ value may be obtained as
kQ=0.0065.times.510=3.4.
Next, as depicted in FIG. 14A and FIG. 14B, when the distance from
the power transmitter 1A to the two power receivers 2A and 2B is
500 mm, the k value and the Q factor are k=0.0029 and Q=510.
That is, because the distance from the power transmitter 1A to the
power receivers 2A and 2B becomes longer from 300 mm to 500 mm, the
degree of coupling of magnetic fields (electromagnetic fields)
becomes lower and the k value reduces from 0.0065 to 0.0029. Note
that the Q factor remains at 510 because the degree of losses in a
magnetic field (electromagnetic field) does not change.
Accordingly, as depicted in FIG. 14A and FIG. 14B, when the
distance from the power transmitter 1A to the two power receivers
2A and 2B is 500 mm, the kQ value may be obtained as
kQ=0.0029.times.510=1.5.
FIG. 15A to FIG. 16B are diagrams for describing a wireless power
transmission method. FIGS. 15A and 15B, and FIGS. 16A and 16B, both
depict a case where the distance from the power transmitter 1A to
the two power receivers 2A and 2B is 300 mm, but differing Q
factors. Note that FIG. 15B and FIG. 16B are diagrams with
normalization assuming that the power ratio of 1:1 is "1.00."
First, referring to FIG. 15A and FIG. 15B, the self-inductances
(Lr) of the power receiving secondary-side resonant coils in the
power receivers 2A and 2B are high, and the k value and the Q
factor are k=0.026 and Q=600. In this case, the kQ value may be
obtained as kQ=0.026.times.600=15.3.
Referring to FIG. 16A and FIG. 16B, the self-inductances (Lr) of
the power receiving secondary-side resonant coils in the power
receivers 2A and 2B are low, and the k value and the Q factor are
k=0.0065 and Q=160. In this case, the kQ value may be obtained as
kQ=0.0065.times.160=1.1.
Note that for example, the k value may be calculated based on
specification information defined between the power transmitter 1A
and the power receiver 2A or 2B and a relative positional
relationship between the power transmitter 1A and the power
receiver 2A or 2B, and the Q factor is predefined depending on each
power receiver.
FIG. 17 is a diagram illustrating one example of a wireless power
supply system 100 of the embodiment.
The wireless power supply system 100 includes one power transmitter
1 and a plurality of power receivers 2A and 2B. Although FIG. 17
illustrates two power receivers 2A and 2B, the wireless power
supply system 100 may further include power receivers having a
configuration similar to that of the power receivers 2A and 2B.
Note that in the following description, the power receivers 2A and
2B and other power receivers are simply referred to as the power
receiver(s) 2 unless otherwise specifically provided.
The power transmitter 1 includes a wireless power transmitting unit
11, a power source unit 12, a control unit 13, a communication unit
14, and a storage unit 15.
The power source unit 12 generates high frequency electric power
and, for example, corresponds to the power source unit 12 described
in FIG. 3. The power source unit 12 has a specific power source
impedance. For example, the power source unit 12 may be a power
source such as a constant voltage source whose output impedance is
matched to 50.OMEGA. or a Hi-Z.OMEGA. power source (constant
current source) having a high output impedance. Note that the power
source unit 12 receives electric power supplied from an external
power source 10.
The control unit 13 controls the power transmitting unit 11, and
the communication unit 14 can communicate with each power receiver.
The communication by the communication unit 14 may use, for
example, a DSSS wireless LAN system based on IEEE 802.11b or use
Bluetooth (registered trademark). An antenna 14A is coupled to the
communication unit 14.
For example, a Central Processing Unit (CPU) chip may be used as
the control unit 13. The control unit 13 includes a grouping unit
13A, a charging time calculating unit 13B, and an adjustment
control unit 13C.
The grouping unit 13A performs a process of grouping the plurality
of power receivers 2 based on kQ values of the plurality of power
receivers 2.
The charging time calculating unit 13B uses a k value and a rated
output (rating capacity (Watt Hour)) of the power receiver 2 to
calculate a time required to charge the power receiver 2 (charging
time). From a k value and a Q factor, the charging time calculating
unit 13B can obtain an efficiency of electric power reception of
the power receiver 2. Because Q factors of the respective power
receiver 2 are transmitted to the power transmitter 1 through
communications, the charging time calculating unit 13B can use the
rated outputs and the k values of the power receivers 2 to
calculate the charging times. Further, the charging time
calculating unit 13B calculates a total charging time that
represents a total of charging times for one or more power
receivers 2 included in each group.
The adjustment control unit 13C transmits, to the power receiver 2
via the communication 14, a command to adjust the adjustment unit
27.
The wireless power transmitting unit 11 corresponds to a coil in a
case of magnetic field resonance, and converts high frequency
electric power supplied from the power source unit 12 into a
magnetic field.
The power receivers 2A and 2B respectively include power receiving
units 21A and 21B, rectifier units 22A and 22B, control units 23A
and 23B, communication units 24A and 24B, batteries 25A and 25B,
storage units 26A and 26B, and adjustment units 27A and 27B.
The control units 23A and 23B are devices that control the power
receivers 2A and 2B, and for example, CPU chips may be used as the
control units 23A and 23B.
The communication units 24A and 24B are devices that implement
wireless communications between the power transmitter 1 and power
receivers 2A and 2B. As described above, for example, communication
circuits that perform communications by a wireless LAN or Bluetooth
(registered trademark) may be used as the communication units 24A
and 24B. Antennas 24A1 and 24B1 are respectively coupled to the
communication units 24A and 24B.
Each of the power receiving units 21A and 21B includes a
secondary-side resonant coil 21a and converts wirelessly
transmitted electric power into an electric current. The rectifier
units 22A and 22B convert the AC current obtained from the power
receiving units 21A and 21B into direct current so as to be usable
in battery charging or in a main body of the device.
The storage units 26A and 26B are memories that store information
such as information about grouping and information that represents
power requirements of the power receivers 2A and 2B. The storage
units 26A and 26B may be internal memories of CPU chips used as the
control units 23A and 23B. Note that the power requirements are
electric powers required for charging the power receivers 2A and
2B.
The adjustment units 27A and 27B respectively adjust angles of the
power receiving units 21A and 21B with respect to the power
receivers 2A and 2B. That is, each of the adjustment units 27A and
27B adjusts the angle of the secondary-side resonant coil 21a.
Driving units such as motors are built in the adjustment units 27A
and 27B that hold the power receiving units 21A and 21B. The
adjustment units 27A and 27B drive the driving units to adjust the
angles of the power receiving units 21A and 21B relative to the
power receivers 2A and 2B.
The adjustment units 27A and 27B adjust the angles based on control
signals, transmitted from the control unit 13 of the power
transmitter 1 via the communication unit 14, the antenna 14A, the
antennas 24A1 and 24B1 and the communication units 24A and 24B and
received by the control units 23A and 23B of the power receivers 2A
and 2B. Note that a specific configuration of each of the
adjustment units 27A and 27B will be described later below with
reference to FIG. 18.
As described above, the power transmitter 1 and the power receivers
2A and 2B perform communications via their respective communication
units 14, 24A and 24B.
Here, through communication performed via the communication unit 14
of the power transmitter 1 and the communication unit 24A or 24B of
the power receiver 2A or 2B, data representing received electric
power of the power receiver 2A or 2B and the like is transmitted to
the power transmitter 1. Further, various signals are communicated
such as control signals for adjusting the adjustment units 27A and
27B to adjust the k values, commands that represent grouping based
on the k values, and commands to turn on/off electric power
reception.
Specifically, for example, via the communication unit 14 of the
power transmitter 1 and the communication units 24A and 24B of the
power receivers 2A and 2B, the Q factors in the respective power
receivers 2A and 2B are communicated to the power transmitter 1
that performs control of wireless electric power transmission.
Note that a transmission system of electric power between the
wireless power transmitting unit 11 and the power receiving unit
21A or 21B is not limited to a system using magnetic field
resonance, but may use a system using electric field resonance,
electromagnetic induction, or electric field induction, for
example.
FIG. 18A to 18C are diagrams illustrating the power receiver 2. The
power receiver 2 illustrated in FIGS. 18A to 18C is a smartphone
terminal device, for example. As illustrated in FIG. 18B, a camera
29 is provided on a side opposite to a side where a display and a
touch panel are provided.
The power receiver 2 includes the adjustment unit 27 for adjusting
the angle of the secondary-side resonant coil 21a with respect to
the power receiver 2. The adjustment unit 27 includes a hinge
mechanism 28 that adjusts the angle of the secondary-side resonant
coil 21a having a rectangular ring shape with respect to the power
receiver 2 and includes a motor 28A that drives the hinge mechanism
28.
The adjustment unit 27 can adjust the angle of the secondary-side
resonant coil 21a from a state in which the secondary-side resonant
coil 21a is housed in the power receiver 2 as illustrated in FIG.
18A to a state where the secondary-side resonant coil 21a stands
with respect to the power receiver 2 as illustrated in FIG.
18C.
Upon receiving, by the communication unit 24, an adjustment control
signal transmitted from the power transmitter 1 via the
communication unit 14, the power receiver drives the adjustment
unit 27.
Next, a case will be described of grouping three or more power
receivers based on kQ values. FIG. 19 is a diagram describing
grouping according to a wireless power transmission method of the
embodiment. Although FIG. 19 illustrates one power transmitter 1A
and six power receivers 2A to 2F, this is merely an example, and
various cases may occur, as a matter of course.
As illustrated in FIG. 19, in the wireless power transmission
method of the embodiment, the kQ values of the six power receivers
2A to 2F are evaluated and used for grouping. First, all the power
receivers 2A to 2F are individually evaluated.
For example, when the kQ value of the power receiver 2A is
evaluated, only the power receiver 2A is turned on and the other
power receivers 2B to 2F are turned off. For example, the switch
213 in the secondary-side resonant coil 21a illustrated in FIG. 5A
is turned off. Then, the k value is measured based on the received
electric power of the power receiver 2A. Then, the k value is
multiplied by the Q factor to calculate the kQ value. Similarly for
the power receivers 2B to 2F, the kQ values are calculated by
turning on only electric power reception of a power receiver to be
measured and turning off electric power reception of the other
power receivers to calculate the k values.
For example, in FIG. 19, the power receivers 2B, 2C and 2F are
grouped into a group GP1, and the power receivers 2A, 2D and 2E are
grouped into a group GP2.
FIG. 20 and FIG. 21 are a flowchart illustrating control contents
of the power transmitter 1. FIG. 22 is a diagram illustrating data
used for grouping. Here, a control process will be described inside
the power transmitter 1 when the power transmitter 1 transmits
electric power to the power receivers 2A and 2B in the wireless
power supply system illustrated in FIG. 17. Although FIG. 17
illustrates the two power receivers 2A and 2B, the system may
include three or more power receivers similar to the power
receivers 2A and 2B in practice.
In the following, the power receiver 2A or 2B or another similar
power receiver is simply referred to as the power receiver 2 as
appropriate. In the following description, it is assumed that the
power receiver 2 includes an adjustment unit 27 similar to the
adjustment units 27A and 27B.
The power transmitter 1 transmits predetermined electric power to
each power receiver 2 for performing test electric power
transmission, and communicates with each power receiver 2 in step
Aa. As a result, each power receiver 2 transmits, to the power
transmitter 1, data that represents the received electric power and
a rated output in step Ba.
The power transmitter 1 calculates initial values k.sub.0 of the k
values of the respective power receivers 2 and calculates an
initial value T.sub.0 of the total charging time, and performs
grouping based on the k.sub.0Q values in step S1.
Here, for example, the k.sub.AQ values are converted into
efficiencies of electric power reception to group the power
receivers 2. As illustrated in FIG. 22, they are grouped into
groups G1 to G10, where efficiencies .eta. (%) of electric power
reception are 90.ltoreq..eta.<100, 80.ltoreq..eta.<90,
70.ltoreq..eta.<80, 60.ltoreq..eta.<70,
50.ltoreq..eta.<60, 40.ltoreq..eta.<50,
30.ltoreq..eta.<40, 20.ltoreq..eta.<30,
10.ltoreq..eta.<20, and 0.ltoreq..eta.<10. That is, the
efficiencies of electric power reception are divided for each 10%
such that they are grouped into 10 groups.
Note that the kQ values are converted into the efficiencies .eta.
of electric power reception by the following formula (4). Hence,
when power receivers are grouped based on their kQ values, the
power receivers are grouped by using the following formula (4) to
convert the kQ values into the efficiencies .eta. of electric power
reception.
.eta. ##EQU00003##
The power transmitter 1 transmits, to each power receiver 2, a
change notification for adjusting the adjustment unit 27 of the
power receiver 2 to change the k value to be the maximum value in
step S2 and step Ab. As a result, each power receiver 2 drives the
adjustment unit 27 to adjust the angle of the secondary-side
resonant coil 21a to obtain an angle at which electric power to be
received from the power transmitter 1 is the maximum.
Upon obtaining the angle at which electric power to be received
from the power transmitter 1 is the maximum, each power receiver 2
sets the adjustment unit 27 to the angle, at which electric power
to be received is the maximum, and transmits, to the power
transmitter 1, a signal that represents the completion of setting
in step Bb.
Upon receiving the signals transmitted in step Bb from the
respective power receivers 2, the power transmitter 1 calculates
the maximum values k.sub.A of the k values of the respective power
receivers 2 and the total charging time T.sub.A to perform grouping
based on the k.sub.AQ values in step S3. That is, the power
receivers 2 are again grouped by using the efficiencies of electric
power reception corresponding to the k.sub.AQ values.
The power transmitter 1 determines, with respect to the total
charging times T.sub.0 and T.sub.A, whether T.sub.0.gtoreq.T.sub.A
is satisfied in step S4.
Upon determining that T.sub.0.gtoreq.T.sub.A is satisfied (YES in
step S4), the power transmitter 1 selects one group and sets
electric power to be transmitted to one or more power receivers 2
included in the selected group in step S5.
Further, at this time, the power transmitter 1 transmits, to each
power receiver 2 in the selected group, a command to change the k
value to be the maximum value in step Ac, and receives, from each
power receiver 2, a signal that represents that the k value has
been changed to the maximum value in step Bc.
Here, it is preferable that the group selected in step S5 is a
group such as a group for large kQ values or a group for the large
number of power receivers 2. Here, for example, a group with the
largest kQ value is selected.
Further, the electric power set in step S5 may be obtained by using
the efficiencies of electric power reception and the rated outputs
of the power receivers 2 included in the selected group.
In order not to transmit the electric power to power receivers 2 in
one or more other groups that are not the group selected in step
S5, the power transmitter 1 turns off, in step S6 and step Ad,
electric power reception of the power receivers 2 in the other
groups that are not the group selected in step S5.
A LC resonant circuit including the secondary-side resonant coil
21a may be turned off to turn off the electric power reception.
Thus, for example, when the secondary-side resonant coil 21a
includes the circuit configuration illustrated in FIG. 5A, the
switch 213 may be turned off.
Note that in step S6 and step Ad, electric power reception of the
power receivers 2 in the group selected in step S5 is turned on.
For example, when the secondary-side resonant coil 21a includes the
circuit configuration illustrated in FIG. 5A, the switch 213 may be
turned on.
In step Bd, upon receiving from each power receiver 2 in the group
selected in step S5, a signal that represents that the electric
power reception is turned on and upon receiving, from each power
receiver 2 in the other groups that are not the group selected in
step S5, a signal that represents that the electric power reception
is turned off, the power transmitter 1 starts to transmit the
electric power in step S7.
The power transmitter 1 determines in step S8 whether there is a
power receiver 2 that has been completely charged among the power
receivers 2 in the group selected in step S5. When receiving in
step Be a charging completion notification from a power receiver 2
completely charged, the power transmitter 1 may determine that
there is a power receiver 2 that has been completely charged (YES
in step S8).
Note that the process of step S8 is repeatedly executed until
determining that there is a power receiver 2 completely charged
(YES in step S8). Upon determining that there is a power receiver 2
completely charged (YES in step S8), the power transmitter 1 causes
the flow to proceed to step S9.
The power transmitter 1 temporarily stops transmitting the electric
power in step S9. This is because it is required to reset the
electric power to be transmitted because there is a power receiver
2 completely charged in the group to which the electric power is
transmitted.
In step S10 and step Ae, the power transmitter 1 turns off electric
power reception of the power receiver 2 completely charged.
The power transmitter 1 determines whether all power receivers 2
have been completely charged in step S11. For example, the
determination process of step S11 may be executed by using
Identifications (IDs) of all the power receivers 2 included in the
group selected in step S5.
Upon determining that all the power receivers 2 have not been
completely charged (NO in step S11), the power transmitter 1 resets
in step S12 the electric power to be transmitted. The power
transmitter 1 may use the efficiencies of electric power reception
and the rated outputs of one or more power receivers 2 remaining in
the selected group to reset the electric power to be
transmitted.
Upon completing the process of step S12, the flow returns to step
S7. As a result, until the power transmitter 1 determines that all
the power receivers 2 have been completely charged (YES in step
S11), the process of steps S7 to S12 is repeatedly performed.
Upon determining that all the power receivers 2 have been
completely charged (YES in step S11), the power transmitter 1
determines whether all groups have been completely charged in step
S13. This is for charging the respective groups in order.
Upon determining that all the groups have not been completely
charged (No in step S13), the power transmitter 1 selects one
group, from among uncharged groups, to turn on electric power
reception of one or more power receivers 2 in the selected group in
step S14. Thereby, a command to turn on the electric power
reception is transmitted from the power transmitter 1 to the power
receivers 2 in the selected group in step Af.
The power transmitter 1 sets in step S15 the electric power to be
transmitted to the power receivers 2 within the selected group.
Further, at this time, the power transmitter 1 transmits, to each
power receiver 2 in the selected group, a command to change the k
value to be the maximum value in step Ac, and receives, from each
power receiver 2, a signal that represents that the k value has
been changed to the maximum value in step Bc.
Upon completing the process of step S15, the power transmitter 1
returns the flow to step S7 to start transmitting the electric
power.
As a result, when charging is performed for all the groups and the
power transmitter 1 determines that all the groups have been
completely charged (YES in step S13), the process series is
completed (END).
Upon determining, with respect to the total charging times T.sub.0
and T.sub.A, that T.sub.0.gtoreq.T.sub.A is not satisfied (NO in
step S4), the power transmitter 1 obtains, for respective groups of
all the groups obtained by the grouping based on k.sub.AQ values in
step S3, change amounts .DELTA.k by which the k values are to be
changed from maximum values k.sub.A to move to groups of which
efficiencies of electric power reception are lower by one in step
S16.
Here, changes of efficiencies of electric power reception, for
changing the maximum efficiencies of electric power reception
obtained by the maximum values k.sub.A to upper limit values of the
groups one level below, may be converted, by use of the formula
(4), into the change amounts .DELTA.k, by which the k values are to
be changed from maximum values k.sub.A.
For example, a change amount .DELTA.k by which the k value is to be
decreased from the maximum value k.sub.A is obtained such that
power receivers 2 included in the group G1 illustrated in FIG. 22
can become included in the group G2. More specifically, for a power
receiver 2 of which the efficiency of electric power reception is
92% when the k value is the maximum value k.sub.A, a change amount
.DELTA.k of the k value required to decrease the efficiency of
electric power to be less than 90%, which is the upper limit value
of the group G2, is obtained.
The power transmitter 1 obtains, for all the power receivers 2 in
all the groups, change amounts .DELTA.k of the k values to
calculate total values for the respective groups. Note that because
the k values and the efficiencies of electric power reception can
be considered to linearly change, the change amounts .DELTA.k of
the k values may be obtained by interpolation using the initial
values k.sub.0 of the k values, the efficiencies of electric power
reception corresponding to the initial values k.sub.0, the maximum
values k.sub.A of the k values, and the efficiencies of electric
power reception corresponding to the maximum values k.sub.A, for
example.
In step S17, the power transmitter 1 selects a group whose average
value is smallest with respect to the change amounts .DELTA.k of
the k values for the respective groups obtained in step S16, and
changes the k values of one or more power receivers 2 in the
selected group.
Then, the power transmitter 1 transmits in step Ac, to the power
receiver(s) 2 in the selected group, a command to change the k
value to the k value obtained by decreasing the change amount
.DELTA.k from the maximum value k.sub.A, and receives in step Bc,
from the power receiver(s) 2, a signal that represents that the k
value has been changed.
Note that in a case where a plurality of power receivers 2 are
included in the selected group, the power transmitter 1 performs
the process of step S17 and Ac for each of the power receivers 2,
and as a result, the power transmitter 1 receives in step Bc, from
each of the power receivers 2, a signal that represents that the k
value has been changed.
As a result, the number of groups is reduced. The number of groups
is reduced in order to reduce the total charging time. Note that in
a case where a plurality of groups whose average value is smallest
with respect to the change amounts .DELTA.k for the respective
groups are present in step S17, the k values may be changed for all
the groups concerned, or the k values may be changed for at least
one of the groups concerned.
Upon receiving the signals transmitted in step Bb from the
respective power receivers 2, the power transmitter 1 calculates
the total charging time T.sub.B corresponding to the k values,
changed by decreasing the k values of the respective power
receivers 2 from the maximum values k.sub.A by the change amounts
.DELTA.k, in step S18.
The power transmitter 1 determines, with respect to the total
charging times T.sub.0 and T.sub.B, whether T.sub.0.gtoreq.T.sub.B
is satisfied in step S19.
Upon determining that T.sub.0.gtoreq.T.sub.B is not satisfied (NO
in step S19), the power transmitter 1 causes the flow to return to
step S16.
Then, the power transmitter 1 obtains, for respective groups of all
the groups obtained, average values of change amounts .DELTA.k by
which the k values are to be changed from maximum values k.sub.A to
move to groups of which levels of efficiencies of electric power
reception are lower by two groups in step S16. At this time, the
change amounts .DELTA.k for changing from the maximum values
k.sub.A to the upper limit values of the groups of which
efficiencies of electric power reception are lower by two groups
may be obtained.
In this way, in a case where T.sub.0.gtoreq.T.sub.B is not
satisfied (NO in step S19) and the flow is returned to step S16,
the level to be decreased in step S16 may be increased one by one
for every time passing through the loop of steps S16 to S19.
That is, for the second loop of steps S16 to S19, the power
transmitter 1 obtains, for the respective groups, the change
amounts .DELTA.k by which the k values are to be changed to move to
the groups of which levels of efficiencies of electric power
reception are lower by two groups. Further, for the third loop of
steps S16 to S19, the power transmitter 1 obtains, for the
respective groups, the change amounts .DELTA.k by which the k
values are to be changed to move to the groups of which levels of
efficiencies of electric power reception are lower by three groups.
Every time the number of times passing through the loop increases,
the levels of the groups may be lowered one by one.
In this way, until satisfying T.sub.0.gtoreq.T.sub.B (YES in step
S19), the process of steps S16 to S19 is repeatedly performed.
Upon determining that T.sub.0.gtoreq.T.sub.A is satisfied (YES in
step S4), the power transmitter 1 causes the flow to proceed to
step S5. Subsequently, the power transmitter 1 executes the process
subsequent to step S5.
FIG. 23 is a flowchart illustrating control contents of each power
receiver 2.
Upon entering an area in which electric power is receivable from
the power transmitter 1, the power receiver 2 receives the electric
power and communicates with the power transmitter 1 in step S31. At
this time, the power receiver 2 receives the predetermined electric
power for test electric power transmission from the power
transmitter 1 in step Aa to measure the received electric
power.
For example, the process of step S31 may be performed by a user of
the power receiver 2 causing the power receiver 2 to approach the
power transmitter 1 while turning on the electric power reception
of the power receiver 2.
The power receiver 2 transmits, to the power transmitter 1 in step
S32 and step Ba, data that represents the received electric power
and the rated output.
The power receiver 2 determines whether a change notification of
the k value has been received from the power transmitter 1 in step
S33. The process of step S33 is repeatedly performed until
receiving a change notification of the k value.
In step Ab, the change notification, which is for adjusting the
adjustment unit 27 to change the k value to the maximum value, is
transmitted from the power transmitter 1 to the power receiver 2.
Upon determining that the change notification has been received
(YES in step S33), the power receiver changes the k value to the
maximum value k.sub.A in step S34. Upon receiving the change
notification, the power receiver 2 adjusts the adjustment unit 27
to search for the angle of the adjustment unit 27 at which the
received electric power becomes the maximum, and sets it to be the
angle that gives the maximum received electric power. This is
because the angle that gives the maximum received electric power is
the angle at which the k value becomes the maximum value
k.sub.A.
Upon completing the setting to the maximum value k.sub.A, the power
receiver 2 transmits in step S35 and step Bb a signal that
represents the completion of the setting.
The power receiver 2 determines whether a command to change the k
value has been received from the power transmitter 1 in step S36.
The process of step S36 is performed in a case where the power
transmitter 1 performs the process of step S5 or step S17.
Accordingly, in step S36, the power receiver 2 determines whether
the command to change the k value based on the process of step S5
or S17 of the power transmitter 1 has been received (step Ac). When
the power transmitter 1 performs the process of step S5, the
command received by the power receiver 2 in step S36 is a command
to set the k value to be the maximum value k.sub.A. When the power
transmitter 1 performs the process of step 17, the command received
by the power receiver 2 in step S36 is a command to set the k value
to be the k value obtained by decreasing from the maximum value
k.sub.A by the change amount .DELTA.k.
Upon determining that a command to change the k value has been
received (YES in step S36), the power receiver 2 changes the k
value in accordance with the command in step S37. Then, the power
receiver 2 transmits, to the power transmitter 1 in step Bc, a
signal that represents that the k value has been changed. Upon
completing the process of step S37, the power receiver 2 causes the
flow to proceed to step S38.
Upon determining that a command to change the k value has not been
received (NO in step S36), the power receiver 2 causes the flow to
proceed to step S38. Note that the case of not receiving from the
power transmitter 1 a command to change the k value (NO in step
S36) is a case where grouping is completed.
The power receiver 2 determines in step S38 whether its k value is
to be changed. More specifically, the power receiver 2 determines
whether the power receiver itself 2 is included in a group to be
supplied with electric power.
The determination as to whether to be supplied with electric power
may be made based on whether either a command to turn off the
electric power reception based on the process of step Ad or a
command to turn on the electric power reception based on the
process of step Af has been received.
In a case of receiving a command to turn off the electric power
reception, the power receiver 2 determines that the power receiver
2 itself is not to be supplied with electric power (NO in step
S38), and turns off the electric power reception in step S39. For
example, when the secondary-side resonant coil 21a includes the
circuit configuration illustrated in FIG. 5A, the switch 213 may be
turned off. The power receiver 2 transmits, to the power
transmitter 1 in step Bd, a signal that represents that the
electric power reception has been turned off.
Note that upon turning off the electric power reception in step
S39, the power receiver returns the flow to step S38. This is for
preparing a case where the power receiver 2 itself is to be
supplied with electric power.
In a case of receiving a command to turn on the electric power
reception, the power receiver 2 determines that the power receiver
2 itself is to be supplied with electric power (YES in step S38),
and turns on the electric power reception in step S39. For example,
when the secondary-side resonant coil 21a includes the circuit
configuration illustrated in FIG. 5A, the switch 213 may be turned
on. The power receiver 2 transmits, to the power transmitter 1 in
step Bd, a signal that represents that the electric power reception
has been turned on.
Upon the power transmitter 1 receiving, from all the power
receivers 2, a signal based on step Bd representing that the
electric power reception has been turned off and a signal based on
step Bd representing that the electric power reception has been
turned on, the power transmitter 1 starts to transmit electric
power and charges one or more power receivers 2 whose electric
power reception has been turned on.
The power receiver 2 determines in step S41 whether the charging
has been completed. The power receiver 2 may determine whether the
charging has been completed based on its rated output, the amount
of electric power reception per unit time, and an elapsed time from
starting of the charging. Upon determining that the charging has
not been completed (NO in step S41), the power receiver 2
repeatedly performs the process of step S41 for each control cycle
of the power receiver 2.
Upon determining that the charging has been completed (YES in step
S41), the power receiver 2 transmits, to the power transmitter 1 in
step S42 and step Be, a signal that represents the completion of
the charging. As a result, the electric power reception of the
power receiver 2 is turned off by the power transmitter 1 in step
Ae.
Upon receiving the command to turn off the electric power reception
from the power transmitter 1 in step Ae, the power receiver 2 turns
off the electric power reception in step S43.
As described above, the charging of the power receiver 2 is
completed. The power receiver 2 repeatedly executes the process of
step S38 until the power receiver 2 itself is to be supplied with
electric power. While the power receiver 2 repeatedly executes the
process of step S38, the power transmitter 1 repeats the process of
steps S7 to S17. Thereby, all the power receivers 2 are
charged.
As described above, according to the embodiment, by performing
grouping based on the kQ values, the total charging time for
charging all power receivers 2 can be shortened.
Therefore, according to the embodiment, it is possible to provide
the wireless power supply system, the power transmitter, and the
power transmission method that can efficiently transmit electric
power.
Note that a process of FIG. 24 or FIG. 25 may be performed instead
of the process of the power transmitter 1 illustrated in FIG.
21.
FIG. 24 is a flowchart illustrating control contents of the power
transmitter 1 according to a first variation example of the
embodiment. The process of FIG. 24 is a process that may be
performed when the number of groups grouped based on the maximum
values k.sub.A in step S3 is greater than the initial number of
groups grouped in step S1 and it is determined in step S4 that
T.sub.0.gtoreq.T.sub.A is not satisfied.
First, the power transmitter 1 sets in step S20 the initial number
of groups obtained by the grouping of step S1 as N.
The power transmitter 1 obtains in step S21 a total charging time
T.sub.B of charging times for respective groups obtained by one or
more ways of grouping satisfying
k.sub.0.ltoreq.k.sub.B.ltoreq.k.sub.A for the k values (k.sub.B) of
all the power receivers 2 among a plurality of ways of grouping all
the power receivers 2 into N groups.
Here, in a case where there is a plurality of ways of grouping
satisfying k.sub.0.ltoreq.k.sub.B.ltoreq.k.sub.A, charging times
for respective groups obtained by each way of grouping are obtained
and a total charging time T.sub.B is obtained as a total of the
charging times of all the groups for each way of grouping.
Accordingly, the number of total charging times T.sub.B obtained is
equal to the number of ways of grouping satisfying
k.sub.0.ltoreq.k.sub.B.ltoreq.k.sub.A.
The power transmitter 1 determines in step S22 whether the number
of ways of grouping such that the total charging time T.sub.B is
the smallest is one.
In a case where the number of ways of grouping is one (YES in step
S22), the power transmitter 1 changes in step S23 the k values of
all the power receivers 2 to k.sub.B obtained for the respective
power receivers 2. Then, the power transmitter 1 transmits, to the
power receivers 2 in the respective groups, commands to change the
k values to k.sub.B.
Note that because the k values (k.sub.B) of the respective power
receivers 2 may all differ, the k values (k.sub.B) are obtained for
the respective power receivers 2 in step S21 and set in step
S23.
In a case of determining that the number of ways of grouping such
that the total charging time is smallest is not one (NO in step
S22), the power transmitter 1 selects in step S24, from among the
plurality of ways of grouping such that the total charging time
T.sub.B is smallest, a way of grouping whose average value of the k
values (k.sub.B) is largest.
Upon completing the process of step S24, the power transmitter 1
causes the flow to proceed to step S23, and changes in step S23 the
k values of all the power receivers 2 to the k values (k.sub.B)
according to the way of grouping selected in step S24.
As described above, by performing grouping based on the kQ values,
the total charging time for charging all the power receivers can be
reduced.
Therefore, according to the embodiment, it is possible to provide
the wireless power supply system, the power transmitter, and the
power transmission method that can efficiently transmit electric
power.
Although the embodiment in which the process illustrated in FIG. 24
is executed instead of the process of FIG. 21 is described here,
the process illustrated in FIG. 24 may be performed when it is
determined that T.sub.0.gtoreq.T.sub.B is not satisfied (NO in step
S19 illustrated in FIG. 21), for example.
FIG. 25 is a flowchart illustrating control contents of the power
transmitter 1 according to a second variation example of the
embodiment. The process of FIG. 25 is a process that may be
performed, instead of the process illustrated in FIG. 23, when it
is determined in step S4 that T.sub.0.gtoreq.T.sub.A is not
satisfied.
In step S25, the power transmitter 1 obtains an average value
P.sub.B of efficiencies of electric power reception and a total
charging time T.sub.B of charging times for respective groups based
on a way of grouping satisfying
k.sub.0.ltoreq.k.sub.B.ltoreq.k.sub.A for the k values (k.sub.B) of
all the power receivers 2 among a plurality of ways of grouping all
the power receivers 2 into a plurality of groups.
In step S26, the power transmitter 1 uses an optimization method to
obtain the way of grouping that makes the largest average value
P.sub.B, which is the way of grouping satisfying
T.sub.0.gtoreq.T.sub.B in the way of grouping obtained in step
S25.
Here, as the way of grouping according to the optimization method,
for example, a way of grouping may be performed using a
metaheuristic (optimization method). Steps according to the
metaheuristic are the following steps 1 to 5.
In step 1, based on the initial values k.sub.0 and the maximum
values k.sub.A, groups to which corresponding power receivers 2 can
belong are determined.
In step 2, total charging times are calculated for cases of all the
ways of grouping.
In step 3, the way(s) of grouping whose total charging time is
shortest is selected.
In step 4, when the number of ways of grouping whose total charging
time is shortest is one, the one way of grouping is the
solution.
In step 5, when there are two or more combinations whose total
charging time is shortest, groups of which efficiency of electric
power reception (average) are compared. Then, a combination, in
which a group with a highest efficiency of electric power reception
is present, may be the solution. Alternatively, a combination with
the largest number of power receivers 2 belonging to a group of
which efficiency of electric power reception is highest may be the
solution.
Upon completing the process of step S26, the power transmitter 1
changes in step S27 the k values of all the power receivers 2 to
the k values (k.sub.B) according to the way of grouping selected in
step S26. At this time, the power transmitter 1 transmits in step
Ac, to the power receivers 2 in the respective groups, commands to
change the k values to k.sub.B.
As described above, by performing grouping based on the kQ values,
the total charging time for charging all the power receivers can be
reduced.
Therefore, according to the embodiment, it is possible to provide
the wireless power supply system, the power transmitter, and the
power transmission method that can efficiently transmit electric
power.
Although the embodiment in which the process illustrated in FIG. 25
is executed instead of the process of FIG. 21 is described here,
the process illustrated in FIG. 25 may be performed when it is
determined that T.sub.0.gtoreq.T.sub.B is not satisfied (NO in step
S19 illustrated in FIG. 21), for example.
FIG. 26 is a diagram illustrating an example of grouping according
to an electric power transmission method of the embodiment. The
grouping described here is the process that is executed by the
power transmitter 1 (see FIG. 17). Here, [1] to [6] indicate
efficiencies of electric power reception and charging times of
respective six power receivers 2 (see FIG. 17).
The group G2 is a group into which power receivers 2 of which
efficiencies of electric power reception are greater than or equal
to 80% and less than 90% are grouped. The group G4 is a group into
which power receivers 2 of which efficiencies of electric power
reception are greater than or equal to 60% and less than 70% are
grouped. The group G6 is a group into which power receivers 2 of
which efficiencies of electric power reception are greater than or
equal to 40% and less than 50% are grouped.
First, the power transmitter 1 calculates initial values k.sub.0 of
the k values for the respective power receivers 2 and an initial
value T.sub.0 of the total charging time to group the power
receivers 2 based on k.sub.0Q values. This corresponds to the
process of step S1 illustrated in FIG. 20, and the power receivers
2 are grouped in an initial state based on the initial values
k.sub.0 of the k values and the initial time T.sub.0 of the total
charging time. Note that the data illustrated in FIG. 22 is used
for the grouping.
In FIG. 26, the power receivers 2 corresponding to [1] and [2] are
grouped into the group G2. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [1] are 89% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [2] are 80% and 10 seconds (s).
Further, the power receivers 2 corresponding to [3] and [4] are
grouped into the group G4. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [3] are 69% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [4] are 60% and 10 seconds (s).
Further, the power receivers 2 corresponding to [5] and [6] are
grouped into the group G6. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [5] are 48% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [6] are 40% and 10 seconds (s).
In such an initial state of grouping, the charging time of the
group G2 is 10 seconds (s), the charging time of the group G4 is 10
seconds (s), and the charging time of the group G6 is 10 seconds
(s). This is because the power receivers 2 are simultaneously
charged in each group, and therefore the charging time for each
group is determined depending on the longest charging time in the
group.
Accordingly, a total charging time of the groups G2, G4, and G6
according to the initial state of grouping is 30 seconds (s).
Next, the power receivers 2 adjust the adjustment units 27 to
change the k values to the maximum values, and the power
transmitter 1 calculates the maximum values k.sub.A and the total
charging time T.sub.A to group the power receivers 2 again. This
corresponds to the process of steps S2 and S3 illustrated in FIG.
20.
Here, upon the k values being changed to the maximum values
k.sub.A, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [1] become
89% and 10 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [2] become 80% and 10 seconds (s). That is, the
efficiencies of electric power reception and the charging times of
the power receivers 2 corresponding to [1] and [2] do not change
from the initial state. This means that the maximum values k.sub.A
have been obtained in the initial state.
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [3] become
80% and 10 seconds (s). That is, the efficiency of electric power
reception increases.
Further, the efficiencies of electric power reception and the
charging times of the power receivers 2 corresponding to [4], [5],
and [6] all become 60% and 10 seconds (s). That is, the
efficiencies of electric power reception increase.
As a result, according to the grouping based on the maximum values
k.sub.A, the power receivers 2 corresponding to [1], [2], and [3]
are grouped into the group G2 and the power receivers 2
corresponding to [4], [5], and [6] are grouped into the group G4.
Further, the charging times of the respective power receivers 2 are
all 10 seconds.
According to the grouping based on the maximum values k.sub.A as
described above, the charging time of the group G2 is 10 seconds
(s) and the charging time of the group G4 is 10 seconds (s).
Accordingly, the total charging time T.sub.A of the groups G2 and
G4 according to the grouping based on the maximum values k.sub.A is
20 seconds (s).
In this way, by increasing the k values from the initial values
k.sub.0 to the maximum values k.sub.A, the total charging time is
shortened from the initial value T.sub.0, which is 30 seconds, to
the total charging time T.sub.A, which is 20 seconds.
FIG. 27 is a diagram illustrating an example of grouping according
to an electric power transmission method of the embodiment.
First, the power transmitter 1 calculates initial values k.sub.0 of
the k values for the respective power receivers 2 and an initial
value T.sub.0 of the total charging time to group the power
receivers 2 based on k.sub.0Q values. This corresponds to the
process of step S1 illustrated in FIG. 20, and the power receivers
2 are grouped in an initial state based on the initial values
k.sub.0 of the k values and the initial time T.sub.0 of the total
charging time. Note that the data illustrated in FIG. 22 is used
for the grouping.
In FIG. 27, the power receivers 2 corresponding to [1], [2], and
[3] are grouped into the group G3. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [1] are 70% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [2] are 70% and 9 seconds (s). The
efficiency of electric power reception and the charging time of the
power receiver 2 corresponding to [3] are 70% and 8 seconds
(s).
Further, the power receivers 2 corresponding to [4], [5], and [6]
are grouped into the group G6. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [4] are 40% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [5] are 40% and 7 seconds (s). The
efficiency of electric power reception and the charging time of the
power receiver 2 corresponding to [6] are 49% and 7 seconds
(s).
In such an initial state of grouping, the charging time of the
group G3 is 10 seconds (s), and the charging time of the group G6
is 10 seconds (s). This is because the power receivers 2 are
simultaneously charged in each group, and therefore the charging
time for the group G3 is determined depending on the longest
charging time of the power receiver 2 corresponding to [1], and the
charging time for the group G6 is determined depending on the
longest charging time of the power receiver 2 corresponding to
[4].
Accordingly, a total charging time of the groups G3 and G6
according to the initial state of grouping is 20 seconds (s).
Next, the power receivers 2 adjust the adjustment units 27 to
change the k values to the maximum values, and the power
transmitter 1 calculates the maximum values k.sub.A and the total
charging time T.sub.A to group the power receivers 2 again. This
corresponds to the process of steps S2 and S3 illustrated in FIG.
20.
Here, upon the k values being changed to the maximum values
k.sub.A, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [1] become
80% and 10 seconds (s), the efficiency of electric power reception
and the charging time of the power receiver 2 corresponding to [2]
become 80% and 9 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [3] become 70% and 8 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [4] become
70% and 10 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [5] become 50% and 7 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [6] become
80% and 7 seconds (s).
As a result, according to the grouping based on the maximum values
k.sub.A, the power receivers 2 corresponding to [1], [2], and [6]
are grouped into the group G2, the power receivers 2 corresponding
to [3] and [4] are grouped into the group G3, and the power
receiver 2 corresponding to [5] is grouped into the group G5.
According to the grouping based on the maximum values k.sub.A as
described above, the charging time of the group G2 is 10 seconds
(s), the charging time of the group G3 is 10 seconds (s), and the
charging time of the group G5 is 7 seconds (s). This is because the
charging time for each group is determined depending on the longest
charging time in the group.
Accordingly, the total charging time T.sub.A of the groups G2, G3,
and G5 according to the grouping based on the maximum values
k.sub.A is 27 seconds (s).
In the case illustrated in FIG. 27, by increasing the k values from
the initial values k.sub.0 to the maximum values k.sub.A, the total
charging time is extended from the initial value T.sub.0, which is
20 seconds, to the total charging time T.sub.A, which is 27
seconds. This corresponds to a case where it has been determined
that T.sub.0.gtoreq.T.sub.A is not satisfied (NO in step S4).
In such a case, for example, the process illustrated in FIG. 24 may
be executed to shorten the total charging time by returning the
number of groups to the number of groups in the initial state. As a
result of executing the process illustrated in FIG. 24, the
efficiency of electric power reception and the charging time of the
power receiver 2 corresponding to [1] become 79% and 10 seconds
(s), the efficiency of electric power reception and the charging
time of the power receiver 2 corresponding to [2] become 79% and 9
seconds (s), and the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [3] become
70% and 8 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [4] become
70% and 10 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [5] become 50% and 7 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [6] become
79% and 7 seconds (s).
As a result, according to the grouping based on the process
illustrated in FIG. 24, the power receivers 2 corresponding to [1],
[2], [3], [4], and [6] are grouped into the group G3 and the power
receiver 2 corresponding to [5] is grouped into the group G5.
According to the grouping as described above, the charging time of
the group G3 is 10 seconds (s), and the charging time of the group
G5 is 7 seconds (s).
Accordingly, the total charging time of the groups G3 and G5
according to the grouping based on the process illustrated in FIG.
24 is 17 seconds (s).
In this way, by performing the grouping according to the process
illustrated in FIG. 24, the total charging time is shortened from
the initial value T.sub.0 (20 seconds) to 17 seconds.
Note that the process of grouping according to the process
illustrated in FIG. 24 from the grouping according to the maximum
values k.sub.A illustrated in FIG. 27 can be treated as the process
of grouping according to the process illustrated in FIG. 21 from
the grouping according to the maximum values k.sub.A.
FIG. 28 is a diagram illustrating all the ways of grouping when the
power receivers 2 are grouped again through the process of FIG. 24
from the grouping based on the maximum values k.sub.A of FIG.
27.
As illustrated in FIG. 27, at the maximum values k.sub.A, the
efficiencies of electric power reception of the six power receivers
2 corresponding to [1], [2], [3], [4], [5], and [6] are
respectively 80%, 80%, 70%, 70%, 50%, and 80%.
Because the six power receivers 2 are grouped into three groups,
combinations for changing the k values are considered in order to
return, through the process of FIG. 24, to two groups that is the
number of groups in the initial state.
As the ways of grouping the six power receivers 2, corresponding to
[1], [2], [3], [4], [5], and [6] and having the efficiencies of
electric power reception at the maximum values k.sub.A as described
above, into two groups 1 and 2, 31 combinations No. 1 to No. 31
illustrated in FIG. 28 are considered.
According to four combinations No. 5, No. 19, No. 21, and No. 22
among the 31 combinations, the six power receivers 2 can be grouped
into two groups by changing the k value of one or more power
receivers 2 of the six power receivers 2. In FIG. 28, "0" is
indicated for No. 5, No. 19, No. 21, and No. 22 because they can be
established. In FIG. 28, "x" is indicated for combinations that
cannot be established.
When No. 5, No. 19, No. 21, and No. 22 are realized, the total
charging times T.sub.B obtained in the process of step S21 are
respectively 17 seconds, 20 seconds, 17 seconds, and 20
seconds.
Accordingly, there are two combinations No. 5 and No. 22 as
combinations of which the total charging time T.sub.B is shortest,
and "NO" is made in the determination process of step S22.
Then, in step S23, a combination is selected of which k.sub.BQ is
higher among the two combinations No. 5 and No. 21.
Here, for the combination of No. 5, the k value of only the power
receiver 2 corresponding to [4] may be adjusted. More specifically,
the efficiency of electric power reception of the power receiver 2
corresponding to [4] may be decreased from 80% to 70%.
With respect to the above, for the combination of No. 21, the k
values of the power receivers 2 corresponding to [4] and [5] are
required to be adjusted. More specifically, the efficiencies of
electric power reception of the power receivers 2 corresponding to
[4] and [5] are required to be decreased from 80% to 79%.
Hence, in step S23, the combination of No. 5 is selected as the
higher k.sub.BQ among the two combinations No. 5 and No. 21.
FIG. 29 is a diagram illustrating an example of grouping according
to an electric power transmission method of the embodiment.
First, the power transmitter 1 calculates initial values k.sub.0 of
the k values for the respective power receivers 2 and an initial
value T.sub.0 of the total charging time to group the power
receivers 2 based on k.sub.0Q values. This corresponds to the
process of step S1 illustrated in FIG. 20, and the power receivers
2 are grouped in an initial state based on the initial values
k.sub.0 of the k values and the initial time T.sub.0 of the total
charging time. Note that the data illustrated in FIG. 22 is used
for the grouping.
In FIG. 27, the power receivers 2 corresponding to [1], [2], and
[3] are grouped into the group G3. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [1] are 70% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [2] are 70% and 9 seconds (s). The
efficiency of electric power reception and the charging time of the
power receiver 2 corresponding to [3] are 70% and 8 seconds
(s).
Further, the power receivers 2 corresponding to [4], [5], and [6]
are grouped into the group G6. The efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [4] are 40% and 10 seconds (s). The efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [5] are 40% and 7 seconds (s). The
efficiency of electric power reception and the charging time of the
power receiver 2 corresponding to [6] are 45% and 7 seconds
(s).
In such an initial state of grouping, the charging time of the
group G3 is 10 seconds (s), and the charging time of the group G6
is 10 seconds (s).
Accordingly, a total charging time of the groups G3 and G6
according to the initial state of grouping is 20 seconds (s).
Next, the power receivers 2 adjust the adjustment units 27 to
change the k values to the maximum values, and the power
transmitter 1 calculates the maximum values k.sub.A and the total
charging time T.sub.A to group the power receivers 2 again. This
corresponds to the process of steps S2 and S3 illustrated in FIG.
20.
Here, upon the k values being changed to the maximum values
k.sub.A, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [1] become
80% and 10 seconds (s), the efficiency of electric power reception
and the charging time of the power receiver 2 corresponding to [2]
become 80% and 9 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [3] become 71% and 8 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [4] become
70% and 10 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [5] become 50% and 7 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [6] become
80% and 7 seconds (s).
As a result, according to the grouping based on the maximum values
k.sub.A, the power receivers 2 corresponding to [1], [2], and [6]
are grouped into the group G2, the power receivers 2 corresponding
to [3] and [4] are grouped into the group G3, and the power
receiver 2 corresponding to [5] is grouped into the group G5.
According to the grouping based on the maximum values k.sub.A as
described above, the charging time of the group G2 is 10 seconds
(s), the charging time of the group G3 is 10 seconds (s), and the
charging time of the group G5 is 7 seconds (s). This is because the
charging time for each group is determined depending on the longest
charging time in the group.
Accordingly, the total charging time T.sub.A of the groups G2, G3,
and G5 according to the grouping based on the maximum values
k.sub.A is 27 seconds (s).
In the case illustrated in FIG. 29, by increasing the k values from
the initial values k.sub.0 to the maximum values k.sub.A, the total
charging time is extended from the initial value T.sub.0, which is
20 seconds, to the total charging time T.sub.A, which is 27
seconds. This corresponds to a case where it has been determined
that T.sub.0.gtoreq.T.sub.A is not satisfied (NO in step S4).
In such a case, when the power receivers 2 are grouped based on the
optimization process illustrated in FIG. 24, the efficiency of
electric power reception and the charging time of the power
receiver 2 corresponding to [1] become 79% and 10 seconds (s), the
efficiency of electric power reception and the charging time of the
power receiver 2 corresponding to [2] become 79% and 9 seconds (s),
and the efficiency of electric power reception and the charging
time of the power receiver 2 corresponding to [3] become 71% and 8
seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [4] become
70% and 10 seconds (s), and the efficiency of electric power
reception and the charging time of the power receiver 2
corresponding to [5] become 50% and 7 seconds (s).
Further, the efficiency of electric power reception and the
charging time of the power receiver 2 corresponding to [6] become
79% and 7 seconds (s).
As a result, according to the grouping based on the optimization
process illustrated in FIG. 24, the power receivers 2 corresponding
to [1], [2], [3], [4], and [6] are grouped into the group G3 and
the power receiver 2 corresponding to [5] is grouped into the group
G5.
According to the grouping based on the optimization process as
described above, the charging time of the group G3 is 10 seconds
(s), and the charging time of the group G5 is 7 seconds (s).
Accordingly, the total charging time of the groups G3 and G5
according to the grouping based on the optimization process
illustrated in FIG. 24 is 17 seconds (s).
In this way, by performing the grouping according to the
optimization, the total charging time is shortened from the initial
value T.sub.0 (20 seconds) to 17 seconds.
FIGS. 30A to 30C are diagrams illustrating a power receiver 2
according to a variation example of the embodiment.
The power receiver 2 illustrated in FIGS. 30A to 30C has a
configuration in which a power extraction coil 21b is added to the
power receiver 2 illustrated in FIG. 18. The power extraction coil
21b receives electric power, through electromagnetic induction,
received by the secondary-side resonant coil 21a from the
primary-side resonant coil 11a of the power transmitter 1 through
magnetic field resonance. Accordingly, in FIGS. 30A to 30C, the
secondary-side resonant coil 21a serves as a relay coil. Note that
a resonant coil that receives electric power through magnetic field
resonance similar to the secondary-side resonant coil 21a may be
used instead of the power extraction coil 21b as an electromagnetic
induction coil.
The power receiver 2 illustrated in FIGS. 30A to 30C can more
easily receive electric power transmitted from the power
transmitter 1 by using the secondary-side resonant coil 21a serving
as a relay coil.
FIGS. 31A and 31B are diagrams illustrating a power receiver 2
according to a variation example of the embodiment.
The power receiver 2 illustrated in FIGS. 31A and 31B is a
smartphone terminal device having a configuration, where the
secondary-side resonant coil 21a of the power receiver 2
illustrated in FIG. 18 is internally contained and the adjustment
unit 27 is omitted. Upon receiving an adjustment control signal for
the k value from the power transmitter 1, the power receiver 2
illustrated in FIG. 18 converts the adjustment amount, which is
based on the adjustment control signal, into a three-dimensional
angle value and displays the adjustment amount of the angle on a
display 29A.
In FIGS. 31A and 31B, a message "PLEASE TILT TO LOWER THE RIGHT
SIDE BY 5 DEGREES" is displayed on the display 29A. A user of the
power receiver 2 adjusts the angle of the power receiver 2
according to the message displayed on the display 29A. Thereby, the
k value is increased and the efficiency of electric power reception
of the power receiver 2 is increased. Power receivers 2 as
illustrated in FIGS. 31A and 31B may be used instead of the power
receivers 2 as illustrated in FIG. 18 to adjust k values as
illustrated in FIGS. 20, 21, 23, 24, and 25.
FIG. 32 is a diagram illustrating a wireless power supply system
100A according to a variation example of the embodiment.
The wireless power supply system 100A has a configuration in which
an adjustment unit 16 is added to the power transmitter 1 of the
wireless power supply system 100 illustrated in FIG. 17. The
adjustment unit 16 is provided in order to adjust, with respect to
the power transmitter 1, an angle of the primary-side resonant coil
11a.
When the coupling coefficients (k values) between the power
transmitter 1 and the power receivers 2A and 2B are adjusted, the
adjustment unit 16 of the power transmitter 1 may be adjusted in
addition to adjusting the adjustment units 27 of the power
receivers 2A and 2B or instead of adjusting the adjustment units 27
of the power receivers 2A and 2B.
Although examples of the wireless power supply system, the power
transmitter, and the power transmission method according to the
embodiment of the present invention have been described above, the
present invention is not limited to the embodiment specifically
disclosed and various variations and modifications may be made
without departing from the scope of the present invention.
All examples and conditional language provided herein are intended
for pedagogical purposes of aiding the reader in understanding the
invention and the concepts contributed by the inventors to further
the art, and are not to be construed as limitation to such
specifically recited examples and conditions, nor does the
organization of such examples in the specification relate to a
showing of superiority and inferiority of the invention. Although
one or more embodiments of the present invention have been
described in detail, it should be understood that various changes,
substitutions, and alterations could be made hereto without
departing from the spirit and scope of the invention.
* * * * *